Re: [gentoo-user] LVM for data drives but not the OS

Re: [gentoo-user] LVM for data drives but not the OS

[Gregory Shearman]

In linux.gentoo.user, you wrote:
> Neil Bothwick wrote:
>> On Thu, 07 Apr 2011 05:22:41 -0500, Dale wrote:
>>
>>    
>>> I want to do it this way because I don't trust LVM enough to put my OS
>>> on.  Just my personal opinion on LVM.
>>>      
>> This doesn't make sense. Your OS can be reinstalled in an hour or two,
>> your photos etc. are irreplaceable.
>>
>>    
>
> It does to me.  I want to keep things so that if there is a problem, I 
> know how to fix it or can at least get to a point that I can get help on 
> it.  If LVM fails and I can't boot, then I loose everything on LVM 
> because I would have to reinstall from scratch.  If it fails just on my 
> data stuff, I can get help and fix it because I can still boot up and 
> get to my email program.  Also, I have the important stuff backed up to 
> DVD.  I would only loose things that I can download again.  I would just 
> rather avoid that and I'm sure AT&T would agree.  That's a lot of 
> downloading.

I have all my partitions on LVM except the boot partition. I've used LVM
for more years than I could count and have *never* had a failure related
to LVM.

I backup my machines to an external drive (2 backup drives actually)
using rsync.

If I have a failure and cannot boot then I just put in my Gentoo Minimal
CD (which has all the LVM tools available) and I can fix the damage. If
the damage isn't fixable then I can just copy over the backups.

LVM snapshots make live backups a breeze. Backups are always in a
consistent state and I've tested them and they *work*.

-- 
Regards,
Gregory.

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Gregory Shearman wrote:
> In linux.gentoo.user, you wrote:
>    
>> Neil Bothwick wrote:
>>      
>>> On Thu, 07 Apr 2011 05:22:41 -0500, Dale wrote:
>>>
>>>
>>>        
>>>> I want to do it this way because I don't trust LVM enough to put my OS
>>>> on.  Just my personal opinion on LVM.
>>>>
>>>>          
>>> This doesn't make sense. Your OS can be reinstalled in an hour or two,
>>> your photos etc. are irreplaceable.
>>>
>>>
>>>        
>> It does to me.  I want to keep things so that if there is a problem, I
>> know how to fix it or can at least get to a point that I can get help on
>> it.  If LVM fails and I can't boot, then I loose everything on LVM
>> because I would have to reinstall from scratch.  If it fails just on my
>> data stuff, I can get help and fix it because I can still boot up and
>> get to my email program.  Also, I have the important stuff backed up to
>> DVD.  I would only loose things that I can download again.  I would just
>> rather avoid that and I'm sure AT&T would agree.  That's a lot of
>> downloading.
>>      
> I have all my partitions on LVM except the boot partition. I've used LVM
> for more years than I could count and have *never* had a failure related
> to LVM.
>
> I backup my machines to an external drive (2 backup drives actually)
> using rsync.
>
> If I have a failure and cannot boot then I just put in my Gentoo Minimal
> CD (which has all the LVM tools available) and I can fix the damage. If
> the damage isn't fixable then I can just copy over the backups.
>
> LVM snapshots make live backups a breeze. Backups are always in a
> consistent state and I've tested them and they *work*.
>
>    

If you know how to do that, then that works.  Right now, I have no 
experience with LVM.  All I know is what I have read which is about as 
clear as mud.  ;-)

Dale

:-)  :-)

P. S.  I wonder why this reply was not threaded with the rest?  I see 
this happen sometimes with other threads.  Always been curious about that.

[gentoo-user] Re: LVM for data drives but not the OS

[James]

Dale <rdalek1967 <at> gmail.com> writes:

> If you know how to do that, then that works.  Right now, I have no 
> experience with LVM.  All I know is what I have read which is about as 
> clear as mud.  

Yes, I agree with you Dale.
The docs on LVM raid and many related issues are
in poor shape, confusing and missing current information.

James

Re: [gentoo-user] LVM for data drives but not the OS

[David W Noon]

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On Fri, 08 Apr 2011 15:50:03 +0200, Dale wrote about Re: [gentoo-user]
LVM for data drives but not the OS:

[snip]
>Ooooh.  Still some progress tho.  lol  So, if I was going to use LVM,
>I create a partition first, either whole drive or part of it then use
>LVM on that?

You use pvcreate to create a physical volume from the partition; this
formats the partition for LVM use, rather than for a filesystem. When
you have enough physical volumes on enough disks -- it's usually one
large PV per disk -- you then use vgcreate to amalgamate those physical
volumes into a volume group.  You can then use lvcreate to allocate
logical volumes within that volume group.

After that, you use mkfs to format each logical volume, as if it were a
partition.  You can then add them to /etc/fstab and mount them as
needed.

Note that the amalgamation of physical volumes into a volume group
allows you to do some neat things: you can "stripe" a logical volume
across multiple physical volumes to improve its I/O bandwidth; your
volume group is what DASD managers call a "concatenation set", which
means its effective size is the sum of the physical volume sizes, so
you can create a logical volume that is bigger than any of the physical
volumes involved.

But before you do any of that fancy stuff, get used to using LVM2 as a
smarter partition manager.
-- 
Regards,

Dave  [RLU #314465]
*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
dwnoon@ntlworld.com (David W Noon)
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[gentoo-user] LVM for data drives but not the OS

[Dale]

Hi,

Quick question about LVM.  I have a 750Gb drive that has miscellaneous 
stuff on it.  Stuff likes videos, music, pictures, ISO files and a few 
other things.  It's not full yet but it is working on it.  I have my OS 
on sda.  The large drive is on sdc.  If I buy another drive it should be 
sdd.  I think this is possible from what I have read but want to make 
sure.  Could I put sdc and sdd on LVM but the OS remain as it is with 
LVM not involved at all?  Basically, my OS stays just like it is and is 
not touched my LVM at all but the two larger drives are managed by LVM.

I want to do it this way because I don't trust LVM enough to put my OS 
on.  Just my personal opinion on LVM.

If there is a better solution to link two large drives, I'm open to 
those ideas as well.  LVM is all I can think of is why I mention it.

Thanks.

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Thursday 07 April 2011 05:22:41 Dale wrote:
> Hi,
> 
> Quick question about LVM.  I have a 750Gb drive that has miscellaneous
> stuff on it.  Stuff likes videos, music, pictures, ISO files and a few
> other things.  It's not full yet but it is working on it.  I have my OS
> on sda.  The large drive is on sdc.  If I buy another drive it should be
> sdd.  I think this is possible from what I have read but want to make
> sure.  Could I put sdc and sdd on LVM but the OS remain as it is with
> LVM not involved at all?  Basically, my OS stays just like it is and is
> not touched my LVM at all but the two larger drives are managed by LVM.

Simple (and complete answer): Yes, you can use LVM only for a subset of the 
drives you have inside a system.

You will need to do it in the following steps though:
- create PV, LVM and LV on the new drive
- copy data over
- create PV on old drive and add it to LVM
Contact me or list if you need help with the actual commands and syntax. 
(There are plenty of howtos around)

> I want to do it this way because I don't trust LVM enough to put my OS
> on.  Just my personal opinion on LVM.

Interesting argument. You don't trust LVM, so you put your personal files on 
there, but not the easily replacable stuff like OS? :)

> If there is a better solution to link two large drives, I'm open to
> those ideas as well.  LVM is all I can think of is why I mention it.

RAID-0 (if they're same size) or linking them together.
Compared to those, I would always recommend LVM as that is easier to maintain 
then JBOD or RAID-0.

There might also be filesystems that include disk-spanning, but if you're 
already not convinced about LVM being reliable, I wouldn't use one of these 
filesystems then.

Please note, I have not lost data related to issues with LVM. I have, in the 
distant past, lost data related to issues with filesystems.
Because of the latter, I rely on a combination of RAID-subsystems with LVM on 
top and reliable backups :)

--
Joost Roeleveld

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Joost Roeleveld wrote:
> On Thursday 07 April 2011 05:22:41 Dale wrote:
>    
>> Hi,
>>
>> Quick question about LVM.  I have a 750Gb drive that has miscellaneous
>> stuff on it.  Stuff likes videos, music, pictures, ISO files and a few
>> other things.  It's not full yet but it is working on it.  I have my OS
>> on sda.  The large drive is on sdc.  If I buy another drive it should be
>> sdd.  I think this is possible from what I have read but want to make
>> sure.  Could I put sdc and sdd on LVM but the OS remain as it is with
>> LVM not involved at all?  Basically, my OS stays just like it is and is
>> not touched my LVM at all but the two larger drives are managed by LVM.
>>      
> Simple (and complete answer): Yes, you can use LVM only for a subset of the
> drives you have inside a system.
>
> You will need to do it in the following steps though:
> - create PV, LVM and LV on the new drive
> - copy data over
> - create PV on old drive and add it to LVM
> Contact me or list if you need help with the actual commands and syntax.
> (There are plenty of howtos around)
>
>    

I was reading the howto on a couple sites and it sounded like this could 
be done.  Glad to know I would have to copy the files over to a LVM 
drive tho.  That info was something I didn't know.  I was hoping for 
some magic.  lol

>> I want to do it this way because I don't trust LVM enough to put my OS
>> on.  Just my personal opinion on LVM.
>>      
> Interesting argument. You don't trust LVM, so you put your personal files on
> there, but not the easily replacable stuff like OS? :)
>
>    

I like my OS setup and don't want to have to reinstall.  Although Gentoo 
has never let me down yet, I don't want to add to the confusion.  If I 
can boot and get to my email, I can get help to fix LVM if needed.  I 
also keep a backup of my personal files.  I could recover the things I 
don't backup tho.  Most of my concern is my lack of experience with 
LVM.  If I was a guru on it, I might feel better about it.

>> If there is a better solution to link two large drives, I'm open to
>> those ideas as well.  LVM is all I can think of is why I mention it.
>>      
> RAID-0 (if they're same size) or linking them together.
> Compared to those, I would always recommend LVM as that is easier to maintain
> then JBOD or RAID-0.
>
> There might also be filesystems that include disk-spanning, but if you're
> already not convinced about LVM being reliable, I wouldn't use one of these
> filesystems then.
>
> Please note, I have not lost data related to issues with LVM. I have, in the
> distant past, lost data related to issues with filesystems.
> Because of the latter, I rely on a combination of RAID-subsystems with LVM on
> top and reliable backups :)
>
> --
> Joost Roeleveld
>
>    

Unless someone has a better idea, I think LVM is about all I can find 
that would do this.  The drives won't be even close to each other.  I 
hope I can find a nice 2Tb drive that I can afford.  ;-)  Maybe that 
will last a while.  The 750Gb drive did last a pretty good while. I'm 
not sure after that tho.

Thanks for the info.  It did add to my knowledge and settle one of my 
questions.

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Thursday 07 April 2011 06:12:40 Dale wrote:
> Joost Roeleveld wrote:
> > On Thursday 07 April 2011 05:22:41 Dale wrote:
> > You will need to do it in the following steps though:
> > - create PV, LVM and LV on the new drive
> > - copy data over
> > - create PV on old drive and add it to LVM
> > Contact me or list if you need help with the actual commands and syntax.
> > (There are plenty of howtos around)
> 
> I was reading the howto on a couple sites and it sounded like this could
> be done.  Glad to know I would have to copy the files over to a LVM
> drive tho.  That info was something I didn't know.  I was hoping for
> some magic.  lol

As far as I know, there is no "automatic conversion tool" for most of these.
Switching from non-raid to RAID-1 (mirroring) is the only one I think that 
might work.

> >> I want to do it this way because I don't trust LVM enough to put my OS
> >> on.  Just my personal opinion on LVM.
> > 
> > Interesting argument. You don't trust LVM, so you put your personal
> > files on there, but not the easily replacable stuff like OS? :)
> 
> I like my OS setup and don't want to have to reinstall.  Although Gentoo
> has never let me down yet, I don't want to add to the confusion.  If I
> can boot and get to my email, I can get help to fix LVM if needed.  I
> also keep a backup of my personal files.  I could recover the things I
> don't backup tho.  Most of my concern is my lack of experience with
> LVM.  If I was a guru on it, I might feel better about it.

Worst case I had: the metadata was incorrect. This was back with 2.6.18 
kernels though.
That was also easily recovered as all the LVM-tools, with default 
configuration, backup the metadata to a text-file before/after making any 
chances.
You can then easily recover if anything goes wrong :)

> > Please note, I have not lost data related to issues with LVM. I have, in
> > the distant past, lost data related to issues with filesystems.
> > Because of the latter, I rely on a combination of RAID-subsystems with
> > LVM on top and reliable backups :)
> > 
> > --
> > Joost Roeleveld
> 
> Unless someone has a better idea, I think LVM is about all I can find
> that would do this.  The drives won't be even close to each other.  I
> hope I can find a nice 2Tb drive that I can afford.  ;-)  Maybe that
> will last a while.  The 750Gb drive did last a pretty good while. I'm
> not sure after that tho.

I've got 6 * 1.5TB drives in RAID-5 for documents and media and we have about 
2TB left. But with our usage, I'll probably have to look into extending that 
later this year.

> Thanks for the info.  It did add to my knowledge and settle one of my
> questions.

Always glad to help.

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[Neil Bothwick]

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On Thu, 07 Apr 2011 05:22:41 -0500, Dale wrote:

> I want to do it this way because I don't trust LVM enough to put my OS 
> on.  Just my personal opinion on LVM.

This doesn't make sense. Your OS can be reinstalled in an hour or two,
your photos etc. are irreplaceable.


-- 
Neil Bothwick

Advanced: (adj.) doesn't work yet, but it's pretty close. See: bug,
glitch.

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Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Neil Bothwick wrote:
> On Thu, 07 Apr 2011 05:22:41 -0500, Dale wrote:
>
>    
>> I want to do it this way because I don't trust LVM enough to put my OS
>> on.  Just my personal opinion on LVM.
>>      
> This doesn't make sense. Your OS can be reinstalled in an hour or two,
> your photos etc. are irreplaceable.
>
>    

It does to me.  I want to keep things so that if there is a problem, I 
know how to fix it or can at least get to a point that I can get help on 
it.  If LVM fails and I can't boot, then I loose everything on LVM 
because I would have to reinstall from scratch.  If it fails just on my 
data stuff, I can get help and fix it because I can still boot up and 
get to my email program.  Also, I have the important stuff backed up to 
DVD.  I would only loose things that I can download again.  I would just 
rather avoid that and I'm sure AT&T would agree.  That's a lot of 
downloading.

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Neil Bothwick]

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On Thu, 07 Apr 2011 06:28:40 -0500, Dale wrote:

> >> I want to do it this way because I don't trust LVM enough to put my
> >> OS on.  Just my personal opinion on LVM.
> >>        
> > This doesn't make sense. Your OS can be reinstalled in an hour or two,
> > your photos etc. are irreplaceable.
> >
> >      
> 
> It does to me.  I want to keep things so that if there is a problem, I 
> know how to fix it or can at least get to a point that I can get help
> on it.  If LVM fails and I can't boot, then I loose everything on LVM 
> because I would have to reinstall from scratch.  If it fails just on my 
> data stuff, I can get help and fix it because I can still boot up and 
> get to my email program.

We have these things called live CDs and webmail :P

Bear in mind that LVM has been around for years. It is proven and
reliable. Once setup, you don't have to touch it, so you can't break
it. The least trustworthy part of your system remains the user.


-- 
Neil Bothwick

First Law of Laboratory Work:
Hot glass looks exactly the same as cold glass.

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Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Neil Bothwick wrote:
> On Thu, 07 Apr 2011 06:28:40 -0500, Dale wrote:
>
>    
>>>> I want to do it this way because I don't trust LVM enough to put my
>>>> OS on.  Just my personal opinion on LVM.
>>>>
>>>>          
>>> This doesn't make sense. Your OS can be reinstalled in an hour or two,
>>> your photos etc. are irreplaceable.
>>>
>>>
>>>        
>> It does to me.  I want to keep things so that if there is a problem, I
>> know how to fix it or can at least get to a point that I can get help
>> on it.  If LVM fails and I can't boot, then I loose everything on LVM
>> because I would have to reinstall from scratch.  If it fails just on my
>> data stuff, I can get help and fix it because I can still boot up and
>> get to my email program.
>>      
> We have these things called live CDs and webmail :P
>
> Bear in mind that LVM has been around for years. It is proven and
> reliable. Once setup, you don't have to touch it, so you can't break
> it. The least trustworthy part of your system remains the user.
>
>
>    

Since I have no experience with LVM, that is the part I am worried 
about.  If I knew everything you, Alan, Joost and others knew, I'd just 
install everything on it and hope for the best.  I'm concerned that if 
something did go wrong and I couldn't get help, I'd loose everything.  I 
don't have any way to back up this much data.  I hate webmail.  I guess 
I could but that would just get on my nerves something bad.

Why is it that whenever I think I have found a good drive that is in the 
1 to 2Tb range, it has awful reviews?  Things like DOA, died after a few 
hours, days or weeks of use.  This has me concerned.  I have yet to have 
a drive go bad but are they making crap nowadays or what?

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Thursday 07 April 2011 07:49:55 Dale wrote:
> Neil Bothwick wrote:
> > On Thu, 07 Apr 2011 06:28:40 -0500, Dale wrote:
> >>>> I want to do it this way because I don't trust LVM enough to put
> >>>> my
> >>>> OS on.  Just my personal opinion on LVM.
> >>> 
> >>> This doesn't make sense. Your OS can be reinstalled in an hour or
> >>> two,
> >>> your photos etc. are irreplaceable.
> >> 
> >> It does to me.  I want to keep things so that if there is a problem, I
> >> know how to fix it or can at least get to a point that I can get help
> >> on it.  If LVM fails and I can't boot, then I loose everything on LVM
> >> because I would have to reinstall from scratch.  If it fails just on
> >> my
> >> data stuff, I can get help and fix it because I can still boot up and
> >> get to my email program.
> > 
> > We have these things called live CDs and webmail :P
> > 
> > Bear in mind that LVM has been around for years. It is proven and
> > reliable. Once setup, you don't have to touch it, so you can't break
> > it. The least trustworthy part of your system remains the user.
> 
> Since I have no experience with LVM, that is the part I am worried
> about.  If I knew everything you, Alan, Joost and others knew, I'd just
> install everything on it and hope for the best.  I'm concerned that if
> something did go wrong and I couldn't get help, I'd loose everything.  I
> don't have any way to back up this much data.  I hate webmail.  I guess
> I could but that would just get on my nerves something bad.

GMails webmail isn't too bad, tbh :)
I agree though, it's difficult to back up all the data and I have actually 
decided to only back-up a subset of what I have on the server.
It also helps to have more then 1 system when something does go wrong. 
Even a small laptop (netbook-style) that can connect is of great help.

I don't think I know everything, but I do tend to be lucky enough to be able 
to find the info I need online. Then again, internet usage is a bit more 
widespread where I live.

> Why is it that whenever I think I have found a good drive that is in the
> 1 to 2Tb range, it has awful reviews?  Things like DOA, died after a few
> hours, days or weeks of use.  This has me concerned.  I have yet to have
> a drive go bad but are they making crap nowadays or what?

Short answer: yes :)
Long answer: the drives are getting a higher density the whole time which 
makes them more difficult to produce.
Also, companies have found it's cheaper to offer free warranty-replacements 
then make more reliable drives in the first place.
Never mind most people only have the computer running for a few hours a day. 
Not like some of us who have them running 24/7 :)

I currently use WD's Green drives in my server and they do tend to be reliable 
as long as they can be kept decently cooled.

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[Neil Bothwick]

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On Thu, 07 Apr 2011 07:49:55 -0500, Dale wrote:

> > Bear in mind that LVM has been around for years. It is proven and
> > reliable. Once setup, you don't have to touch it, so you can't break
> > it. The least trustworthy part of your system remains the user.

> Since I have no experience with LVM, that is the part I am worried 
> about.  If I knew everything you, Alan, Joost and others knew, I'd just 
> install everything on it and hope for the best.  I'm concerned that if 
> something did go wrong and I couldn't get help, I'd loose everything.
> I don't have any way to back up this much data.  I hate webmail.  I
> guess I could but that would just get on my nerves something bad.

In that case, set up a small physical volume and create a volume group
that holds nothing important. Do you best to break it and only when you
fail should you consider putting anything of any importance on there.


-- 
Neil Bothwick

Any sufficiently advanced bug is indistinguishable from a feature.

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Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Thursday 07 April 2011 14:04:05 Neil Bothwick wrote:
> On Thu, 07 Apr 2011 07:49:55 -0500, Dale wrote:
> > > Bear in mind that LVM has been around for years. It is proven and
> > > reliable. Once setup, you don't have to touch it, so you can't break
> > > it. The least trustworthy part of your system remains the user.
> > 
> > Since I have no experience with LVM, that is the part I am worried
> > about.  If I knew everything you, Alan, Joost and others knew, I'd just
> > install everything on it and hope for the best.  I'm concerned that if
> > something did go wrong and I couldn't get help, I'd loose everything.
> > I don't have any way to back up this much data.  I hate webmail.  I
> > guess I could but that would just get on my nerves something bad.
> 
> In that case, set up a small physical volume and create a volume group
> that holds nothing important. Do you best to break it and only when you
> fail should you consider putting anything of any importance on there.

Eeerh... Neil....
I think Dale will probably succeed in breaking it :)

Dale, this comment isn't meant as an insult. I honestly think you would be 
perfect for some QA or Testing job :)

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[Neil Bothwick]

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On Thu, 07 Apr 2011 15:21:33 +0200, Joost Roeleveld wrote:

> I think Dale will probably succeed in breaking it :)
> 
> Dale, this comment isn't meant as an insult. I honestly think you would
> be perfect for some QA or Testing job :)

But not on any project you wanted to finish on time ;-)


-- 
Neil Bothwick

Blessed be the pessimist for he hath made backups.

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Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Thursday 07 April 2011 14:31:43 Neil Bothwick wrote:
> On Thu, 07 Apr 2011 15:21:33 +0200, Joost Roeleveld wrote:
> > I think Dale will probably succeed in breaking it :)
> > 
> > Dale, this comment isn't meant as an insult. I honestly think you would
> > be perfect for some QA or Testing job :)
> 
> But not on any project you wanted to finish on time ;-)

LOL :)
Seriously, if all the Open Source developers would make the software reliable 
enough to pass his testing methods, there wouldn't be any grounds for 
discussion :)
It would just work, always....

--
Joost

PS. I actually enjoy having people on the list with different levels and types 
of experience. I think I probably learn more stuff via questions from so-called 
"beginners" then from the "old-timers" ;)

Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Thursday 07 April 2011 15:41:00 Joost Roeleveld wrote:
> On Thursday 07 April 2011 14:31:43 Neil Bothwick wrote:
> > On Thu, 07 Apr 2011 15:21:33 +0200, Joost Roeleveld wrote:
> > > I think Dale will probably succeed in breaking it :)
> > > 
> > > Dale, this comment isn't meant as an insult. I honestly think you
> > > would
> > > be perfect for some QA or Testing job :)
> > 
> > But not on any project you wanted to finish on time ;-)
> 
> LOL :)
> Seriously, if all the Open Source developers would make the software
> reliable enough to pass his testing methods, there wouldn't be any grounds
> for discussion :)
> It would just work, always....
> 
> --
> Joost
> 
> PS. I actually enjoy having people on the list with different levels and
> types of experience. I think I probably learn more stuff via questions from
> so-called "beginners" then from the "old-timers" ;)

Actually, thinking about it.
Dale, please do try what Neil suggested. Preferably also document what you do 
so we have a few test cases :)

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Joost Roeleveld wrote:
> On Thursday 07 April 2011 15:41:00 Joost Roeleveld wrote:
>    
>> On Thursday 07 April 2011 14:31:43 Neil Bothwick wrote:
>>      
>>> On Thu, 07 Apr 2011 15:21:33 +0200, Joost Roeleveld wrote:
>>>        
>>>> I think Dale will probably succeed in breaking it :)
>>>>
>>>> Dale, this comment isn't meant as an insult. I honestly think you
>>>> would
>>>> be perfect for some QA or Testing job :)
>>>>          
>>> But not on any project you wanted to finish on time ;-)
>>>        
>> LOL :)
>> Seriously, if all the Open Source developers would make the software
>> reliable enough to pass his testing methods, there wouldn't be any grounds
>> for discussion :)
>> It would just work, always....
>>
>> --
>> Joost
>>
>> PS. I actually enjoy having people on the list with different levels and
>> types of experience. I think I probably learn more stuff via questions from
>> so-called "beginners" then from the "old-timers" ;)
>>      
> Actually, thinking about it.
> Dale, please do try what Neil suggested. Preferably also document what you do
> so we have a few test cases :)
>
> --
> Joost
>
>
>    

I did this many years ago.  When I built my very first rig, I installed 
Mandriva.  Don't shoot me, I hadn't heard of Gentoo yet.  I only knew 
about Redhat and Mandriva at the time.  Anyway, I had one heck of a time 
installing the nvidia drivers.  Lots of people had issues where their 
GUI wouldn't come back up when they installed the drivers.  So, since I 
was a "fool" at the time, I made notes and such as to how I did mine.  
When it worked, I did a howto on it from a "fools" point of view.  I put 
it on about three different sites.  LQ, JL and one other one.  It had a 
HUGE amount of views.  If followed, it worked.  I think me explaining 
from a beginners perspective helped a lot of people, plus I tried to 
keep it simple, like me.  lol

I think some of the reason I haven't grasped LVM is that it is somewhat 
complicated and it is explained by folks that know the nuts and bolts of 
it.  It's like explaining Gentoo Linux to a windoze user who has never 
seen Linux or even knows what a kernel is.

I'm still looking up howtos in hope of having a light bulb moment.  I'll 
have one, it's just a matter of when.

Alex, I saw your post.  I read it a couple times already and am trying 
to grasp it before replying.  It has a lot of good info.  May take me a 
bit.

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Thursday 07 April 2011 09:11:35 Dale wrote:
> Joost Roeleveld wrote:
> > On Thursday 07 April 2011 15:41:00 Joost Roeleveld wrote:
> >> On Thursday 07 April 2011 14:31:43 Neil Bothwick wrote:
> >>> On Thu, 07 Apr 2011 15:21:33 +0200, Joost Roeleveld wrote:
> >>>> I think Dale will probably succeed in breaking it :)
> >>>> 
> >>>> Dale, this comment isn't meant as an insult. I honestly think you
> >>>> would
> >>>> be perfect for some QA or Testing job :)
> >>> 
> >>> But not on any project you wanted to finish on time ;-)
> >> 
> >> LOL :)
> >> Seriously, if all the Open Source developers would make the software
> >> reliable enough to pass his testing methods, there wouldn't be any
> >> grounds for discussion :)
> >> It would just work, always....
> >> 
> >> --
> >> Joost
> >> 
> >> PS. I actually enjoy having people on the list with different levels
> >> and
> >> types of experience. I think I probably learn more stuff via questions
> >> from so-called "beginners" then from the "old-timers" ;)
> > 
> > Actually, thinking about it.
> > Dale, please do try what Neil suggested. Preferably also document what
> > you do so we have a few test cases :)
> > 
> > --
> > Joost
> 
> I did this many years ago.  When I built my very first rig, I installed
> Mandriva.  Don't shoot me,

Why would I? :)
I first played with Linux in 1997.
First distro I tried was slackware and then Redhat.
When redhat started moving more towards Gnome, and I was hit by rpm-
dependencies once too many, I started looking.
It was then that I noticed Gentoo and after a bit of playing with it, moved to 
Gentoo fully.
If, at that time, Ubuntu had been around, I might have missed Gentoo 
alltogether.

> I hadn't heard of Gentoo yet.  I only knew
> about Redhat and Mandriva at the time.  Anyway, I had one heck of a time
> installing the nvidia drivers.  Lots of people had issues where their
> GUI wouldn't come back up when they installed the drivers.  So, since I
> was a "fool" at the time, I made notes and such as to how I did mine.
> When it worked, I did a howto on it from a "fools" point of view.  I put
> it on about three different sites.  LQ, JL and one other one.  It had a
> HUGE amount of views.  If followed, it worked.  I think me explaining
> from a beginners perspective helped a lot of people, plus I tried to
> keep it simple, like me.  lol

Simple-worded howtos tend to be the best.
Unfortunately, people who really know and understand the subject tend to 
become unable to properly word it all in such a way that mere mortals 
understand it as well.

> I think some of the reason I haven't grasped LVM is that it is somewhat
> complicated and it is explained by folks that know the nuts and bolts of
> it.  It's like explaining Gentoo Linux to a windoze user who has never
> seen Linux or even knows what a kernel is.

Hmm... I've given up on those conversations ;)
I'll simply wait till people get curious about what I'm doing with computers 
and why I never complain about them crashing all the time ;)

> I'm still looking up howtos in hope of having a light bulb moment.  I'll
> have one, it's just a matter of when.

Well... I'm confident that light bulb can be lit...

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Neil Bothwick wrote:
> On Thu, 07 Apr 2011 15:21:33 +0200, Joost Roeleveld wrote:
>
>    
>> I think Dale will probably succeed in breaking it :)
>>
>> Dale, this comment isn't meant as an insult. I honestly think you would
>> be perfect for some QA or Testing job :)
>>      
> But not on any project you wanted to finish on time ;-)
>
>
>    


Joost, I see your point.  This is my life saying.  If it wasn't for bad 
luck, I wouldn't have any luck at all.  I hope for the best but expect 
the worst.  You should see my dining room.  Full of food stuff just in 
case.  After my last visit to the grocery store, I'm thinking I may not 
have enough yet.  o_O  I also have a generator and some gas stored too.  
I also have a big garden to grow food as well.  I may be disabled but I 
ain't stupid.  I just try to keep the bad things that can happen in the 
back of my mind and keep a plan going, just in case it does hit the fan.

I'm sort of wanting to use this as a learning experience.  If I can get 
things set up, working and understand what the heck things do, then I 
may try some more stuff.  Right now, my light bulb is pretty dim on 
LVM.  I don't understand how it works and what the heck those commands 
do.  I'll have my light bulb moment eventually.  Since I don't have the 
new drive ordered yet, I got time to read, listen and try to grasp it all.

Just a old dog trying to learn new tricks.  lol

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Thursday 07 April 2011 08:57:40 Dale wrote:
> Neil Bothwick wrote:
> > On Thu, 07 Apr 2011 15:21:33 +0200, Joost Roeleveld wrote:
> >> I think Dale will probably succeed in breaking it :)
> >> 
> >> Dale, this comment isn't meant as an insult. I honestly think you
> >> would
> >> be perfect for some QA or Testing job :)
> > 
> > But not on any project you wanted to finish on time ;-)
> 
> Joost, I see your point.  This is my life saying.  If it wasn't for bad
> luck, I wouldn't have any luck at all.  I hope for the best but expect
> the worst.  You should see my dining room.  Full of food stuff just in
> case.  After my last visit to the grocery store, I'm thinking I may not
> have enough yet.  o_O  I also have a generator and some gas stored too.
> I also have a big garden to grow food as well.  I may be disabled but I
> ain't stupid.  I just try to keep the bad things that can happen in the
> back of my mind and keep a plan going, just in case it does hit the fan.

The Internet is a mixed blessing. We only see what people type. But have 
difficulty understanding their personal situation because we don't see it.
Up untill the point you mentioned you're disabled, I was like "Hmm... I know a 
few people like that :) "
I would call that self-sufficient and quite clever. I would like to be able to 
move somewhere where I could just enjoy life and life of some piece of land.

I would not consider you stupid, you've shown, at least in my opinion, that 
you're not :)

> I'm sort of wanting to use this as a learning experience.  If I can get
> things set up, working and understand what the heck things do, then I
> may try some more stuff.  Right now, my light bulb is pretty dim on
> LVM.  I don't understand how it works and what the heck those commands
> do.  I'll have my light bulb moment eventually.  Since I don't have the
> new drive ordered yet, I got time to read, listen and try to grasp it all.

The beginning of wisdom is admitting you don't have it ;)

> Just a old dog trying to learn new tricks.  lol

I'm lousy at training dogs (or other animals), but lets see if I can make LVM, 
or at least the way I use it, a bit clearer.
If anything isn't clear, please ask.

We've already discussed the benefits of using it in a previous thread. So I'll 
just skip those for now.

With LVM, you end up with 1 or more VGs (Volume Group)
Each VG consists of 1 or more PV (Physical Volume)
Each VG can contain 1 or more LV (Logical Volume)

In simple graphic:
PV <-> VG <-> LV

A PV is either an entire physical disk or a partition on a physical disk. This 
is why they're called "Physical Volume"

A VG is a collection of Physical Volumes. The size of this depends equals the 
total size of all the PVs in this group.

An LV is a partition on this Volume Group.

Now, here comes the nice part. It is possible to extend a VG and LV.
A VG is extended by adding a PV. It can also be reduced in size by removing a 
PV.
NOTE: when removing a PV, ensure it is not used. (Tools exist for this)

An LV can be extended as long as the VG has room for this. No movement of LVs 
is necessary, just like files on a filesystem, they get spread over available 
space.
NOTE: Yes, this does lead to fragmentation (Tools exist to assist in 
defragmenting LVM)
You can also reduce the size of an LV. (Again, make sure reducing the LV in 
size does not lead to loss of data)

On top of an LV, any filesystem (Ext2/3/4, Reiserfs, XFS, JFS,....) can be 
placed. Once an LV is created, the filesystem tools can simply access it just 
like any other block device (eg. physical disk)

When selecting a filesystem to put on top of an LV, do check wether or not it 
at least supports increasing the size after creation. Most filesystems in use 
do support this even while the filesystem is mounted.
Reducing the size of the filesystem is, in my use, less common. And I tend to 
simply copy data to a temporary location when I do need to reduce the size.

I hope the above makes it a bit clearer on how it "works".

The actual commands for creating and managing an LVM-system, I'll leave for 
another time if and when they are needed.

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Joost Roeleveld wrote:
> On Thursday 07 April 2011 08:57:40 Dale wrote:
>    
>> Neil Bothwick wrote:
>>      
>>> On Thu, 07 Apr 2011 15:21:33 +0200, Joost Roeleveld wrote:
>>>        
>>>> I think Dale will probably succeed in breaking it :)
>>>>
>>>> Dale, this comment isn't meant as an insult. I honestly think you
>>>> would
>>>> be perfect for some QA or Testing job :)
>>>>          
>>> But not on any project you wanted to finish on time ;-)
>>>        
>> Joost, I see your point.  This is my life saying.  If it wasn't for bad
>> luck, I wouldn't have any luck at all.  I hope for the best but expect
>> the worst.  You should see my dining room.  Full of food stuff just in
>> case.  After my last visit to the grocery store, I'm thinking I may not
>> have enough yet.  o_O  I also have a generator and some gas stored too.
>> I also have a big garden to grow food as well.  I may be disabled but I
>> ain't stupid.  I just try to keep the bad things that can happen in the
>> back of my mind and keep a plan going, just in case it does hit the fan.
>>      
> The Internet is a mixed blessing. We only see what people type. But have
> difficulty understanding their personal situation because we don't see it.
> Up untill the point you mentioned you're disabled, I was like "Hmm... I know a
> few people like that :) "
> I would call that self-sufficient and quite clever. I would like to be able to
> move somewhere where I could just enjoy life and life of some piece of land.
>
> I would not consider you stupid, you've shown, at least in my opinion, that
> you're not :)
>
>    
>> I'm sort of wanting to use this as a learning experience.  If I can get
>> things set up, working and understand what the heck things do, then I
>> may try some more stuff.  Right now, my light bulb is pretty dim on
>> LVM.  I don't understand how it works and what the heck those commands
>> do.  I'll have my light bulb moment eventually.  Since I don't have the
>> new drive ordered yet, I got time to read, listen and try to grasp it all.
>>      
> The beginning of wisdom is admitting you don't have it ;)
>
>    
>> Just a old dog trying to learn new tricks.  lol
>>      
> I'm lousy at training dogs (or other animals), but lets see if I can make LVM,
> or at least the way I use it, a bit clearer.
> If anything isn't clear, please ask.
>
> We've already discussed the benefits of using it in a previous thread. So I'll
> just skip those for now.
>
> With LVM, you end up with 1 or more VGs (Volume Group)
> Each VG consists of 1 or more PV (Physical Volume)
> Each VG can contain 1 or more LV (Logical Volume)
>
> In simple graphic:
> PV<->  VG<->  LV
>
> A PV is either an entire physical disk or a partition on a physical disk. This
> is why they're called "Physical Volume"
>
> A VG is a collection of Physical Volumes. The size of this depends equals the
> total size of all the PVs in this group.
>
> An LV is a partition on this Volume Group.
>
> Now, here comes the nice part. It is possible to extend a VG and LV.
> A VG is extended by adding a PV. It can also be reduced in size by removing a
> PV.
> NOTE: when removing a PV, ensure it is not used. (Tools exist for this)
>
> An LV can be extended as long as the VG has room for this. No movement of LVs
> is necessary, just like files on a filesystem, they get spread over available
> space.
> NOTE: Yes, this does lead to fragmentation (Tools exist to assist in
> defragmenting LVM)
> You can also reduce the size of an LV. (Again, make sure reducing the LV in
> size does not lead to loss of data)
>
> On top of an LV, any filesystem (Ext2/3/4, Reiserfs, XFS, JFS,....) can be
> placed. Once an LV is created, the filesystem tools can simply access it just
> like any other block device (eg. physical disk)
>
> When selecting a filesystem to put on top of an LV, do check wether or not it
> at least supports increasing the size after creation. Most filesystems in use
> do support this even while the filesystem is mounted.
> Reducing the size of the filesystem is, in my use, less common. And I tend to
> simply copy data to a temporary location when I do need to reduce the size.
>
> I hope the above makes it a bit clearer on how it "works".
>
> The actual commands for creating and managing an LVM-system, I'll leave for
> another time if and when they are needed.
>
> --
> Joost
>
>    

I'm going to give this a stab here.  I go buy a new drive. I use cfdisk 
to make it ready for LVM, the 8E thingy.  I then tell LVM to make it a 
Physical Volume, either in whole or in part.  I then tell LVM to make it 
a Volume Group and if I already had a drive using LVM I could then add 
the new drive to it.  After that, I create Logical Volumes and put file 
systems on it for use sort of like the old partitions.

Am I sort of getting on the right track?

Did someone mention a GUI for this?   ^-^

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Alan McKinnon]

Apparently, though unproven, at 18:25 on Friday 08 April 2011, Dale did opine 
thusly:

> I'm going to give this a stab here.  I go buy a new drive. I use cfdisk 
> to make it ready for LVM, the 8E thingy.  

Yes

> I then tell LVM to make it a 
> Physical Volume, either in whole or in part.  

Yes

> I then tell LVM to make it 
> a Volume Group 

No.

You add the PV to a Volume Group (which will be created if necessary)

> and if I already had a drive using LVM I could then add 
> the new drive to it.  

Yes. 

> After that, I create Logical Volumes and put file 
> systems on it for use sort of like the old partitions.

Yes. Once you have made the LV, you then do this:

mkfs /dev/mapper/<whatever>

instead of 

mkfs /dev/sda1

The kernel sees /dev/mapper/<whatever> as just another block device (aka 
something it can mkfs)

> 
> Am I sort of getting on the right track?

Spot on

> Did someone mention a GUI for this?   ^-^

Piffle. GUIs for LVM confuse the issue. Stay away from them like the plague.




-- 
alan dot mckinnon at gmail dot com

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Alan McKinnon wrote:
> Apparently, though unproven, at 18:25 on Friday 08 April 2011, Dale did opine
> thusly:
>
>    
>> I'm going to give this a stab here.  I go buy a new drive. I use cfdisk
>> to make it ready for LVM, the 8E thingy.
>>      
> Yes
>
>    
>> I then tell LVM to make it a
>> Physical Volume, either in whole or in part.
>>      
> Yes
>
>    
>> I then tell LVM to make it
>> a Volume Group
>>      
> No.
>
> You add the PV to a Volume Group (which will be created if necessary)
>
>    

Yea, I didn't type that in the way I meant it.  PV is the bottom level, 
then VG goes on top of that then the LV.  I think I am typing that in 
right.  Basically, I create the PV first, then the VG then the LV. < 
scratches head a bit>  I think I get it but may need better wording.

>> and if I already had a drive using LVM I could then add
>> the new drive to it.
>>      
> Yes.
>
>    
>> After that, I create Logical Volumes and put file
>> systems on it for use sort of like the old partitions.
>>      
> Yes. Once you have made the LV, you then do this:
>
> mkfs /dev/mapper/<whatever>
>
> instead of
>
> mkfs /dev/sda1
>
> The kernel sees /dev/mapper/<whatever>  as just another block device (aka
> something it can mkfs)
>
>    

So when I get ready to make a file system, say ext3, then it would be 
mkfs.ext3 /dev/mapper/<whatever>.  Then it would be ready to put stuff on.

>> Am I sort of getting on the right track?
>>      
> Spot on
>
>    
>> Did someone mention a GUI for this?   ^-^
>>      
> Piffle. GUIs for LVM confuse the issue. Stay away from them like the plague.
>
>    

That is likely a good idea too.  I get used to the GUI then if the GUI 
can't work, maybe X won't come up or something, then I have no idea 
where to start.  Good advice.

Thanks.

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Alan McKinnon]

Apparently, though unproven, at 19:39 on Friday 08 April 2011, Dale did opine 
thusly:

[snip]


> Yea, I didn't type that in the way I meant it.  PV is the bottom level,
> then VG goes on top of that then the LV.  I think I am typing that in
> right.  Basically, I create the PV first, then the VG then the LV. <
> scratches head a bit>  I think I get it but may need better wording.

Nah, you got it already ;-)

> > The kernel sees /dev/mapper/<whatever>  as just another block device (aka
> > something it can mkfs)
> 
> So when I get ready to make a file system, say ext3, then it would be
> mkfs.ext3 /dev/mapper/<whatever>.  Then it would be ready to put stuff on.

Yup. You'll have to poke around /dev/ a bit to see how your udev does it today 
but you got the gist of it


-- 
alan dot mckinnon at gmail dot com

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Alan McKinnon wrote:
> Apparently, though unproven, at 19:39 on Friday 08 April 2011, Dale did opine
> thusly:
>
> [snip]
>
>
>    
>> Yea, I didn't type that in the way I meant it.  PV is the bottom level,
>> then VG goes on top of that then the LV.  I think I am typing that in
>> right.  Basically, I create the PV first, then the VG then the LV.<
>> scratches head a bit>   I think I get it but may need better wording.
>>      
> Nah, you got it already ;-)
>
>    
>>> The kernel sees /dev/mapper/<whatever>   as just another block device (aka
>>> something it can mkfs)
>>>        
>> So when I get ready to make a file system, say ext3, then it would be
>> mkfs.ext3 /dev/mapper/<whatever>.  Then it would be ready to put stuff on.
>>      
> Yup. You'll have to poke around /dev/ a bit to see how your udev does it today
> but you got the gist of it
>
>
>    


root@fireball / # pvcreate /dev/sdb
   Physical volume "/dev/sdb" successfully created
root@fireball / #

Step one done.  It didn't puke on my keyboard.  lol

Now to see what else I can get into.  Not going to put anything 
important on it tho.  Just a temporary thing right now.  Just getting my 
feet wet.

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Dale wrote:
>
>
> root@fireball / # pvcreate /dev/sdb
>   Physical volume "/dev/sdb" successfully created
> root@fireball / #
>
> Step one done.  It didn't puke on my keyboard.  lol
>
> Now to see what else I can get into.  Not going to put anything 
> important on it tho.  Just a temporary thing right now.  Just getting 
> my feet wet.
>
> Dale
>
> :-)  :-)
>

More progress.

root@fireball / # ls -al /dev/mapper/
total 0
drwxr-xr-x  2 root root      80 Apr  8 15:56 .
drwxr-xr-x 16 root root    4400 Apr  8 15:56 ..
crw-rw----  1 root root 10, 236 Apr  8 04:39 control
lrwxrwxrwx  1 root root       7 Apr  8 15:56 sdb--vg-test -> ../dm-0
root@fireball / # pvdisplay
   --- Physical volume ---
   PV Name               /dev/sdb
   VG Name               sdb-vg
   PV Size               232.83 GiB / not usable 2.58 MiB
   Allocatable           yes
   PE Size               4.00 MiB
   Total PE              59604
   Free PE               46804
   Allocated PE          12800
   PV UUID               kopUKm-lXy1-7tiq-FuQ2-Xhs5-tGqN-Ls4R1v

root@fireball / # vgdisplay
   --- Volume group ---
   VG Name               sdb-vg
   System ID
   Format                lvm2
   Metadata Areas        1
   Metadata Sequence No  2
   VG Access             read/write
   VG Status             resizable
   MAX LV                0
   Cur LV                1
   Open LV               0
   Max PV                0
   Cur PV                1
   Act PV                1
   VG Size               232.83 GiB
   PE Size               4.00 MiB
   Total PE              59604
   Alloc PE / Size       12800 / 50.00 GiB
   Free  PE / Size       46804 / 182.83 GiB
   VG UUID               5OSiWZ-rWza-uKJ2-rVMO-f38G-NBHx-dmAE1K

root@fireball / # lvdisplay
   --- Logical volume ---
   LV Name                /dev/sdb-vg/test
   VG Name                sdb-vg
   LV UUID                mixhOb-La6D-BwG4-Uz3l-P0ci-oGg5-YI3mN8
   LV Write Access        read/write
   LV Status              available
   # open                 0
   LV Size                50.00 GiB
   Current LE             12800
   Segments               1
   Allocation             inherit
   Read ahead sectors     auto
   - currently set to     256
   Block device           254:0

root@fireball / #

I'm still trying to figure out how the naming part works tho.  Now to 
mount it and put something on it.  See if it works.

Let me know if something doesn't look right.  Otherwise, I'll keep 
playing around with it.

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[J. Roeleveld]

On Fri, April 8, 2011 11:01 pm, Dale wrote:
> Dale wrote:
>>
>>
>> root@fireball / # pvcreate /dev/sdb
>>   Physical volume "/dev/sdb" successfully created
>> root@fireball / #
>>
>> Step one done.  It didn't puke on my keyboard.  lol
>>
>> Now to see what else I can get into.  Not going to put anything
>> important on it tho.  Just a temporary thing right now.  Just getting
>> my feet wet.
>>
>> Dale
>>
>> :-)  :-)
>>
>
> More progress.
>
> root@fireball / # ls -al /dev/mapper/
> total 0
> drwxr-xr-x  2 root root      80 Apr  8 15:56 .
> drwxr-xr-x 16 root root    4400 Apr  8 15:56 ..
> crw-rw----  1 root root 10, 236 Apr  8 04:39 control
> lrwxrwxrwx  1 root root       7 Apr  8 15:56 sdb--vg-test -> ../dm-0

Looks good :)

> root@fireball / # pvdisplay
>    --- Physical volume ---
>    PV Name               /dev/sdb
>    VG Name               sdb-vg
>    PV Size               232.83 GiB / not usable 2.58 MiB
>    Allocatable           yes
>    PE Size               4.00 MiB
>    Total PE              59604
>    Free PE               46804
>    Allocated PE          12800
>    PV UUID               kopUKm-lXy1-7tiq-FuQ2-Xhs5-tGqN-Ls4R1v

Looks fine

> root@fireball / # vgdisplay
>    --- Volume group ---
>    VG Name               sdb-vg
>    System ID
>    Format                lvm2
>    Metadata Areas        1
>    Metadata Sequence No  2
>    VG Access             read/write
>    VG Status             resizable
>    MAX LV                0
>    Cur LV                1
>    Open LV               0
>    Max PV                0
>    Cur PV                1
>    Act PV                1
>    VG Size               232.83 GiB
>    PE Size               4.00 MiB
>    Total PE              59604
>    Alloc PE / Size       12800 / 50.00 GiB
>    Free  PE / Size       46804 / 182.83 GiB
>    VG UUID               5OSiWZ-rWza-uKJ2-rVMO-f38G-NBHx-dmAE1K

Looks ok, 50GB of 232.83 assigned

> root@fireball / # lvdisplay
>    --- Logical volume ---
>    LV Name                /dev/sdb-vg/test
>    VG Name                sdb-vg
>    LV UUID                mixhOb-La6D-BwG4-Uz3l-P0ci-oGg5-YI3mN8
>    LV Write Access        read/write
>    LV Status              available
>    # open                 0
>    LV Size                50.00 GiB
>    Current LE             12800
>    Segments               1
>    Allocation             inherit
>    Read ahead sectors     auto
>    - currently set to     256
>    Block device           254:0

Here is the 50GB...

> root@fireball / #
>
> I'm still trying to figure out how the naming part works tho.  Now to
> mount it and put something on it.  See if it works.

Naming part, there are 2 ways of finding it.
1: /dev/<VolumeGroupName>/<LogicalVolumeName>
2: /dev/mapper/<VolumeGroupName>-<LogicalVolumeName>

You included a "-" in your VG-name, this is replaced with "--" under
/dev/mapper/

> Let me know if something doesn't look right.  Otherwise, I'll keep
> playing around with it.

Looks fine so far, don't forget to put a filesystem on "/dev/sdb-vg/test"
to be able to mount it somewhere :)

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

J. Roeleveld wrote:
> On Fri, April 8, 2011 11:01 pm, Dale wrote:
>    
>
>> root@fireball / #
>>
>> I'm still trying to figure out how the naming part works tho.  Now to
>> mount it and put something on it.  See if it works.
>>      
> Naming part, there are 2 ways of finding it.
> 1: /dev/<VolumeGroupName>/<LogicalVolumeName>
> 2: /dev/mapper/<VolumeGroupName>-<LogicalVolumeName>
>
> You included a "-" in your VG-name, this is replaced with "--" under
> /dev/mapper/
>
>    
>> Let me know if something doesn't look right.  Otherwise, I'll keep
>> playing around with it.
>>      
> Looks fine so far, don't forget to put a filesystem on "/dev/sdb-vg/test"
> to be able to mount it somewhere :)
>
> --
> Joost
>
>    

The naming I was talking about was sort of like a label.  I wanted to 
use test, where I might use say data in real use, but ended up with this:

root@fireball / # df
Filesystem           1K-blocks      Used Available Use% Mounted on
<< SNIP >>
/dev/mapper/sdb--vg-test
                       51606140    184268  48800432   1% /mnt/temp
root@fireball / #

I don't mind the sdb--vg part tho.  I guess that sort of points to what 
all is needed to get to that point.  Might come in handy if I needed to 
remove something tho.  Sort of tells me what is what.

I did try to mount it before putting a file system on it.  I sort of 
missed that part somewhere.  I knew it needed it, just forgot to do it.  
Mount sort of puked on my keyboard to remind me.  lol

Whew !!  Progress.  Oh, someone posted a link to a site that had 
pictures.  That helped a good bit.  It needed more detail tho.  I'm 
going to do some google image searches and see what I can find.

Thanks much.

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Friday 08 April 2011 16:30:03 Dale wrote:
> J. Roeleveld wrote:
> > On Fri, April 8, 2011 11:01 pm, Dale wrote:
> >> root@fireball / #
> >> 
> >> I'm still trying to figure out how the naming part works tho.  Now to
> >> mount it and put something on it.  See if it works.
> > 
> > Naming part, there are 2 ways of finding it.
> > 1: /dev/<VolumeGroupName>/<LogicalVolumeName>
> > 2: /dev/mapper/<VolumeGroupName>-<LogicalVolumeName>
> > 
> > You included a "-" in your VG-name, this is replaced with "--" under
> > /dev/mapper/
> > 
> >> Let me know if something doesn't look right.  Otherwise, I'll keep
> >> playing around with it.
> > 
> > Looks fine so far, don't forget to put a filesystem on
> > "/dev/sdb-vg/test"
> > to be able to mount it somewhere :)
> > 
> > --
> > Joost
> 
> The naming I was talking about was sort of like a label.  I wanted to
> use test, where I might use say data in real use, but ended up with this:
> 
> root@fireball / # df
> Filesystem           1K-blocks      Used Available Use% Mounted on
> << SNIP >>
> /dev/mapper/sdb--vg-test
>                        51606140    184268  48800432   1% /mnt/temp
> root@fireball / #
> 
> I don't mind the sdb--vg part tho.  I guess that sort of points to what
> all is needed to get to that point.  Might come in handy if I needed to
> remove something tho.  Sort of tells me what is what.

True :)
I tend to start my VGs with "vg_<something>". That way I know what they're 
for.
Also, it's a good idea to not name them "vg" as then you can get naming 
conflicts if you ever put the drive into another machine that also has a VG 
called that.

As example for the way I name them:
vg_<hostname>.
On my server, I actually have 2 Volume Groups. One for the OS-parts (including 
VMs) and the other for the data.

> I did try to mount it before putting a file system on it.  I sort of
> missed that part somewhere.  I knew it needed it, just forgot to do it.
> Mount sort of puked on my keyboard to remind me.  lol

Hehe :)
I forget as well sometimes.

> Whew !!  Progress.  Oh, someone posted a link to a site that had
> pictures.  That helped a good bit.  It needed more detail tho.  I'm
> going to do some google image searches and see what I can find.

I think I posted more then 1 link, actually :)

> Thanks much.

You're welcome

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Joost Roeleveld wrote:
> On Friday 08 April 2011 16:30:03 Dale wrote:
>    
>>
>> The naming I was talking about was sort of like a label.  I wanted to
>> use test, where I might use say data in real use, but ended up with this:
>>
>> root@fireball / # df
>> Filesystem           1K-blocks      Used Available Use% Mounted on
>> <<  SNIP>>
>> /dev/mapper/sdb--vg-test
>>                         51606140    184268  48800432   1% /mnt/temp
>> root@fireball / #
>>
>> I don't mind the sdb--vg part tho.  I guess that sort of points to what
>> all is needed to get to that point.  Might come in handy if I needed to
>> remove something tho.  Sort of tells me what is what.
>>      
> True :)
> I tend to start my VGs with "vg_<something>". That way I know what they're
> for.
> Also, it's a good idea to not name them "vg" as then you can get naming
> conflicts if you ever put the drive into another machine that also has a VG
> called that.
>
> As example for the way I name them:
> vg_<hostname>.
> On my server, I actually have 2 Volume Groups. One for the OS-parts (including
> VMs) and the other for the data.
>
>    

I wish it was like file system labels but I guess any clues is better 
than nothing.


>> I did try to mount it before putting a file system on it.  I sort of
>> missed that part somewhere.  I knew it needed it, just forgot to do it.
>> Mount sort of puked on my keyboard to remind me.  lol
>>      
> Hehe :)
> I forget as well sometimes.
>
>    
>> Whew !!  Progress.  Oh, someone posted a link to a site that had
>> pictures.  That helped a good bit.  It needed more detail tho.  I'm
>> going to do some google image searches and see what I can find.
>>      
> I think I posted more then 1 link, actually :)
>
>    
>> Thanks much.
>>      
> You're welcome
>
> --
> Joost
>    

You did.  I think a couple of them had some pictures to but google image 
search found some more that helped.  Of course, reading the commands to 
see how they work helped too.  I just needed a picture to see how this 
was built up.

I learned a lot in the past couple days.  Still don't want my OS on it 
tho.  ;-)

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Neil Bothwick]

[-- Attachment #1: Type: text/plain, Size: 543 bytes --]

On Sat, 09 Apr 2011 08:00:49 -0500, Dale wrote:

> I wish it was like file system labels but I guess any clues is better 
> than nothing.

It is like filesystem labels in that you can give VGs and LVs meaningful
names. You can use filesystem labels too, if you feel the need. A logical
volume is just a block device, like /dev/sda1, you can do the same to
either in terms of filesystems.


-- 
Neil Bothwick

"You know how dumb the average person is? Well, statistically, half of
them are even dumber than that" - Lewton, P.I.

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Re: [gentoo-user] LVM for data drives but not the OS

[Alan McKinnon]

Apparently, though unproven, at 23:01 on Friday 08 April 2011, Dale did opine 
thusly:

> Dale wrote:
> > root@fireball / # pvcreate /dev/sdb
> > 
> >   Physical volume "/dev/sdb" successfully created
> > 
> > root@fireball / #
> > 
> > Step one done.  It didn't puke on my keyboard.  lol
> > 
> > Now to see what else I can get into.  Not going to put anything
> > important on it tho.  Just a temporary thing right now.  Just getting
> > my feet wet.
> > 
> > Dale
> > 
> > :-)  :-)
> 
> More progress.
> 
> root@fireball / # ls -al /dev/mapper/
> total 0
> drwxr-xr-x  2 root root      80 Apr  8 15:56 .
> drwxr-xr-x 16 root root    4400 Apr  8 15:56 ..
> crw-rw----  1 root root 10, 236 Apr  8 04:39 control
> lrwxrwxrwx  1 root root       7 Apr  8 15:56 sdb--vg-test -> ../dm-0
> root@fireball / # pvdisplay
>    --- Physical volume ---
>    PV Name               /dev/sdb
>    VG Name               sdb-vg
>    PV Size               232.83 GiB / not usable 2.58 MiB
>    Allocatable           yes
>    PE Size               4.00 MiB
>    Total PE              59604
>    Free PE               46804
>    Allocated PE          12800
>    PV UUID               kopUKm-lXy1-7tiq-FuQ2-Xhs5-tGqN-Ls4R1v
> 
> root@fireball / # vgdisplay
>    --- Volume group ---
>    VG Name               sdb-vg
>    System ID
>    Format                lvm2
>    Metadata Areas        1
>    Metadata Sequence No  2
>    VG Access             read/write
>    VG Status             resizable
>    MAX LV                0
>    Cur LV                1
>    Open LV               0
>    Max PV                0
>    Cur PV                1
>    Act PV                1
>    VG Size               232.83 GiB
>    PE Size               4.00 MiB
>    Total PE              59604
>    Alloc PE / Size       12800 / 50.00 GiB
>    Free  PE / Size       46804 / 182.83 GiB
>    VG UUID               5OSiWZ-rWza-uKJ2-rVMO-f38G-NBHx-dmAE1K
> 
> root@fireball / # lvdisplay
>    --- Logical volume ---
>    LV Name                /dev/sdb-vg/test
>    VG Name                sdb-vg
>    LV UUID                mixhOb-La6D-BwG4-Uz3l-P0ci-oGg5-YI3mN8
>    LV Write Access        read/write
>    LV Status              available
>    # open                 0
>    LV Size                50.00 GiB
>    Current LE             12800
>    Segments               1
>    Allocation             inherit
>    Read ahead sectors     auto
>    - currently set to     256
>    Block device           254:0
> 
> root@fireball / #
> 
> I'm still trying to figure out how the naming part works tho.  Now to
> mount it and put something on it.  See if it works.

Naming can vary a lot depending on udev rules. There will be one canonical 
name and one or more other things that symlink to it.

Likely the canonical stuff will be /dev/mapper/.....
and the symlinks will be in /dev/sdb-vg/.....
cd and ls will see you right :-)


 
> Let me know if something doesn't look right.  Otherwise, I'll keep
> playing around with it.

Cool. So now you have a 250G PV, and it's the the only PV in it's volume 
group. You've made a 50G LV called "test"

Cool so far. Now make a few more LVs (check the man pages, I'm doing this from 
memory):

lvcreate -L 20G -n test2 sdb-vg
lvcreate -L 30G -n test3 sdb-vg

mkfs them:
mkfs.<your_choice> /dev/sdb-vg/test{,2,3}

mount points:
mkdir /mnt/test{,2,3}

mount them:
mount /dev/sdb-vg/test /mnt/test

Whoop-dee-doo. Now you can copy stuff there and do whatever you do with 
filesystems. Let's assume you have music on the first one "test". Let's also 
assume you get more music and it's more than 50G; say you need another 20. 
Easy-peasy, grow the filesystem, grow the LV:

lvextend -L +20G /dev/sdb-vg/test
resize2fs /dev/sdb-vg/test

That's it. Nothing more. Without LVM, you'd be off down to the 'puter store 
looking to buy 70 CDs to do that :-)

It's important to remember that once you've made /dev/sdb into a PV, you will 
never touch that device again. You will especially never fdisk or mkfs it - 
all that is done on the block device that LVM gives you - /dev/sdb-vg/test



-- 
alan dot mckinnon at gmail dot com

Re: [gentoo-user] LVM for data drives but not the OS

[Neil Bothwick]

[-- Attachment #1: Type: text/plain, Size: 423 bytes --]

On Fri, 8 Apr 2011 23:23:20 +0200, Alan McKinnon wrote:

> Cool so far. Now make a few more LVs (check the man pages, I'm doing
> this from memory):
> 
> lvcreate -L 20G -n test2 sdb-vg
> lvcreate -L 30G -n test3 sdb-vg

A little time saver, if you have only one VG, set $LVM_VG_NAME to its
name and you can leave the VG name out of any lv* commands.


-- 
Neil Bothwick

"Criminal Lawyer" is a redundancy.

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Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Neil Bothwick wrote:
> On Fri, 8 Apr 2011 23:23:20 +0200, Alan McKinnon wrote:
>
>    
>> Cool so far. Now make a few more LVs (check the man pages, I'm doing
>> this from memory):
>>
>> lvcreate -L 20G -n test2 sdb-vg
>> lvcreate -L 30G -n test3 sdb-vg
>>      
> A little time saver, if you have only one VG, set $LVM_VG_NAME to its
> name and you can leave the VG name out of any lv* commands.
>
>
>    

I'll have more than one before long so may as well learn the long way.  
Neat to know tho.  I'm hoping for about a 2Tb or maybe a 1.5Tb drive.  
That should last me a while but I'm going to put my current 750Gb on 
there too.

My new rig is still growing.  lol

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

OK.  I learned something.  Check this out:

root@fireball / # df
Filesystem           1K-blocks      Used Available Use% Mounted on
<< SNIP >>
/dev/mapper/sdb--vg-test
                       51606140  48910048     74652 100% /mnt/temp
root@fireball / #

This is what I am doing here.  As I posted a while ago, I created a 50Gb 
LV.  I attempted to copy about 75Gbs to it which filled it up but I 
wanted to make sure it would.  lol  Then I used lvextend -L100G 
/dev/mapper/sdb--vg-test to make it larger.  I read I could do the same 
thing with lvresize but the example I was reading showed lvextend.  This 
is what I got now:

root@fireball / # lvdisplay
   --- Logical volume ---
   LV Name                /dev/sdb-vg/test
   VG Name                sdb-vg
   LV UUID                mixhOb-La6D-BwG4-Uz3l-P0ci-oGg5-YI3mN8
   LV Write Access        read/write
   LV Status              available
   # open                 1
   LV Size                100.00 GiB
   Current LE             25600
   Segments               1
   Allocation             inherit
   Read ahead sectors     auto
   - currently set to     256
   Block device           254:0

root@fireball / #

So, according to that it is 100Gbs which is what I wanted.  Thing was, 
it didn't work.  So, hmmmm.  Light bulb moment.  Resize the file system 
silly.  After that, success.  So, I created something that wasn''t big 
enough, filled it up, made it bigger, fixed the file system and now it 
is working.  All while online too.  That is the weird part.

Still not comfy putting a OS on it but it is cool so far.

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Saturday 09 April 2011 00:28:20 Dale wrote:
> OK.  I learned something.  Check this out:
> 
> root@fireball / # df
> Filesystem           1K-blocks      Used Available Use% Mounted on
> << SNIP >>
> /dev/mapper/sdb--vg-test
>                        51606140  48910048     74652 100% /mnt/temp
> root@fireball / #
> 
> This is what I am doing here.  As I posted a while ago, I created a 50Gb
> LV.  I attempted to copy about 75Gbs to it which filled it up but I
> wanted to make sure it would.  lol  Then I used lvextend -L100G
> /dev/mapper/sdb--vg-test to make it larger.  I read I could do the same
> thing with lvresize but the example I was reading showed lvextend.  This
> is what I got now:
> 
> root@fireball / # lvdisplay
>    --- Logical volume ---
>    LV Name                /dev/sdb-vg/test
>    VG Name                sdb-vg
>    LV UUID                mixhOb-La6D-BwG4-Uz3l-P0ci-oGg5-YI3mN8
>    LV Write Access        read/write
>    LV Status              available
>    # open                 1
>    LV Size                100.00 GiB
>    Current LE             25600
>    Segments               1
>    Allocation             inherit
>    Read ahead sectors     auto
>    - currently set to     256
>    Block device           254:0
> 
> root@fireball / #
> 
> So, according to that it is 100Gbs which is what I wanted.  Thing was,
> it didn't work.  So, hmmmm.  Light bulb moment.  Resize the file system
> silly.  After that, success.  So, I created something that wasn''t big
> enough, filled it up, made it bigger, fixed the file system and now it
> is working.  All while online too.  That is the weird part.
> 
> Still not comfy putting a OS on it but it is cool so far.

Nice :)

Btw, instead of specifying "final" size after resizing, you can actually tell 
it to "add" 20GB by doing:
lvrextend -L+20G /dev/sdb-vg/test

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Joost Roeleveld wrote:
>
> Nice :)
>
> Btw, instead of specifying "final" size after resizing, you can actually tell
> it to "add" 20GB by doing:
> lvrextend -L+20G /dev/sdb-vg/test
>
> --
> Joost
>
>
>    

So that was what the howto meant.  If I know the total I need then I can 
specify it but if I know the amount of extra space I need, I can just do 
+XX and it adds it.  That's neat.  Some coder had his/her thinking hat 
on that day.

Thanks.

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Saturday 09 April 2011 08:04:19 Dale wrote:
> Joost Roeleveld wrote:
> > Nice :)
> > 
> > Btw, instead of specifying "final" size after resizing, you can actually
> > tell it to "add" 20GB by doing:
> > lvrextend -L+20G /dev/sdb-vg/test
> > 
> > --
> > Joost
> 
> So that was what the howto meant.  If I know the total I need then I can
> specify it but if I know the amount of extra space I need, I can just do
> +XX and it adds it.  That's neat.  Some coder had his/her thinking hat
> on that day.

For completeness, I just want to add that if there is not sufficient space 
available in the VG. The command will fail with a message telling you there is 
not enough room :)

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[Neil Bothwick]

[-- Attachment #1: Type: text/plain, Size: 585 bytes --]

On Fri, 08 Apr 2011 18:36:28 -0500, Dale wrote:

> > A little time saver, if you have only one VG, set $LVM_VG_NAME to its
> > name and you can leave the VG name out of any lv* commands.

> I'll have more than one before long so may as well learn the long way.  
> Neat to know tho.  I'm hoping for about a 2Tb or maybe a 1.5Tb drive.  
> That should last me a while but I'm going to put my current 750Gb on 
> there too.

No matter how many drives you have, I doubt you'll need more than one
volume group.


-- 
Neil Bothwick

Top Oxymorons Number 7: Definite maybe

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Re: [gentoo-user] LVM for data drives but not the OS

[Peter Humphrey]

On Saturday 09 April 2011 09:52:01 Neil Bothwick wrote:

> No matter how many drives you have, I doubt you'll need more than one
> volume group.

...although I did find not long ago that a second VG for another, temporary 
distro kept things tidy.. This is not to contradict you though.

-- 
Rgds
Peter

Re: [gentoo-user] LVM for data drives but not the OS

[Neil Bothwick]

[-- Attachment #1: Type: text/plain, Size: 743 bytes --]

On Sat, 9 Apr 2011 10:43:12 +0100, Peter Humphrey wrote:

> > No matter how many drives you have, I doubt you'll need more than one
> > volume group.  
> 
> ...although I did find not long ago that a second VG for another,
> temporary distro kept things tidy.. This is not to contradict you
> though.

Oh yes, and I have two VGs on my desktop, because I want to keep backups
completely separate. But for the usage Dale has mentioned, one VG is
best. If for no other reason that multiple VGs reduce the flexibility of
LVM.


-- 
Neil Bothwick

We've all heard that a million monkeys banging on a million
typewriters will eventually reproduce the works of Shakespeare.
Now, thanks to the Internet, we know this is not true.

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Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Neil Bothwick wrote:
> On Sat, 9 Apr 2011 10:43:12 +0100, Peter Humphrey wrote:
>
>    
>>> No matter how many drives you have, I doubt you'll need more than one
>>> volume group.
>>>        
>> ...although I did find not long ago that a second VG for another,
>> temporary distro kept things tidy.. This is not to contradict you
>> though.
>>      
> Oh yes, and I have two VGs on my desktop, because I want to keep backups
> completely separate. But for the usage Dale has mentioned, one VG is
> best. If for no other reason that multiple VGs reduce the flexibility of
> LVM.
>
>
>    

And I wouldn't put another distro on here anyway.  I wuv my Gentoo. < 
dale hugs the Gentoo bytes on the drive platters >  lol  I think for me, 
just one would be enough.

One more question.  When I buy another drive, I use pvcreate to get the 
new drive ready for LVM.  What command adds it to the VG?  Is it 
vgcreate with some option?  I was sort of looking for something like 
vgadd or something but no luck finding that.  Maybe I am missing it on 
the howtos.

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Dale wrote:
> Neil Bothwick wrote:
>> On Sat, 9 Apr 2011 10:43:12 +0100, Peter Humphrey wrote:
>>
>>>> No matter how many drives you have, I doubt you'll need more than one
>>>> volume group.
>>> ...although I did find not long ago that a second VG for another,
>>> temporary distro kept things tidy.. This is not to contradict you
>>> though.
>> Oh yes, and I have two VGs on my desktop, because I want to keep backups
>> completely separate. But for the usage Dale has mentioned, one VG is
>> best. If for no other reason that multiple VGs reduce the flexibility of
>> LVM.
>>
>>
>
> And I wouldn't put another distro on here anyway.  I wuv my Gentoo. < 
> dale hugs the Gentoo bytes on the drive platters >  lol  I think for 
> me, just one would be enough.
>
> One more question.  When I buy another drive, I use pvcreate to get 
> the new drive ready for LVM.  What command adds it to the VG?  Is it 
> vgcreate with some option?  I was sort of looking for something like 
> vgadd or something but no luck finding that.  Maybe I am missing it on 
> the howtos.
>
> Dale
>
> :-)  :-)
>

That would be vgextend wouldn't it?  I just read another bit in another 
howto.

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Alan McKinnon]

Apparently, though unproven, at 12:48 on Saturday 09 April 2011, Dale did 
opine thusly:

> > the new drive ready for LVM.  What command adds it to the VG?  Is it 
> > vgcreate with some option?  I was sort of looking for something like 
> > vgadd or something but no luck finding that.  Maybe I am missing it on 
> > the howtos.
> > 
> > Dale
> > 
> > :-)  :-)
> 
> That would be vgextend wouldn't it?  I just read another bit in another 
> howto.

Yes.

PVs, VGs, LVs all have a concept of extend|resize|reduce. What that means 
depends on what you are working with, but they all make the thing bigger or 
smaller.

For a PV it means the underlying device's size changed, so the PV must change 
to match. Take a 500G drive, create 1 partition on it of 100G and make it a 
PV. Now enlarge the partition to 200G, you must extend the PV to match.

A VG isn't a single thing, it's a collection of things. Extending it means to 
add more PVs, reducing it means to take PVs out of the VG. Hopefully you will 
always remember to migrate the data off a PV before removing it from a VG :-)

Extend/Reduce an LV means to make the device larger/smaller. It is exactly the 
same thing as changing a partition size using fdisk. Obviously, you need to 
tweak the filesystem at the same time

-- 
alan dot mckinnon at gmail dot com

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Alan McKinnon wrote:
> Apparently, though unproven, at 12:48 on Saturday 09 April 2011, Dale did
> opine thusly:
> Yes.
>
> PVs, VGs, LVs all have a concept of extend|resize|reduce. What that means
> depends on what you are working with, but they all make the thing bigger or
> smaller.
>
> For a PV it means the underlying device's size changed, so the PV must change
> to match. Take a 500G drive, create 1 partition on it of 100G and make it a
> PV. Now enlarge the partition to 200G, you must extend the PV to match.
>
> A VG isn't a single thing, it's a collection of things. Extending it means to
> add more PVs, reducing it means to take PVs out of the VG. Hopefully you will
> always remember to migrate the data off a PV before removing it from a VG :-)
>
> Extend/Reduce an LV means to make the device larger/smaller. It is exactly the
> same thing as changing a partition size using fdisk. Obviously, you need to
> tweak the filesystem at the same time
>
>    


So, when I get me a new drive, I use pvcreate to get it ready for LVM, 
then use vgextend to add it to the VG, then it is available for whatever 
LV I want to extend or to make a new LV?

I think I am catching on here.  It was just difficult for me to grasp 
how things are layered for some reason.  Some of the pictures I found 
helped a good bit tho.  Just helped me picture what the commands are 
doing exactly.

I did learn the hard way to resize the file system tho.  I forgot that 
earlier.  Sort of had me scratching my head for a bit.  lol

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Saturday 09 April 2011 06:43:25 Dale wrote:
> Alan McKinnon wrote:
> > Apparently, though unproven, at 12:48 on Saturday 09 April 2011, Dale
> > did
> > opine thusly:
> > Yes.
> > 
> > PVs, VGs, LVs all have a concept of extend|resize|reduce. What that
> > means
> > depends on what you are working with, but they all make the thing bigger
> > or smaller.
> > 
> > For a PV it means the underlying device's size changed, so the PV must
> > change to match. Take a 500G drive, create 1 partition on it of 100G
> > and make it a PV. Now enlarge the partition to 200G, you must extend
> > the PV to match.
> > 
> > A VG isn't a single thing, it's a collection of things. Extending it
> > means to add more PVs, reducing it means to take PVs out of the VG.
> > Hopefully you will always remember to migrate the data off a PV before
> > removing it from a VG :-)
> > 
> > Extend/Reduce an LV means to make the device larger/smaller. It is
> > exactly the same thing as changing a partition size using fdisk.
> > Obviously, you need to tweak the filesystem at the same time
> 
> So, when I get me a new drive, I use pvcreate to get it ready for LVM,
> then use vgextend to add it to the VG, then it is available for whatever
> LV I want to extend or to make a new LV?
> 
> I think I am catching on here.  It was just difficult for me to grasp
> how things are layered for some reason.  Some of the pictures I found
> helped a good bit tho.  Just helped me picture what the commands are
> doing exactly.
> 
> I did learn the hard way to resize the file system tho.  I forgot that
> earlier.  Sort of had me scratching my head for a bit.  lol

That's an easy one to miss :)

You do seem to be catching on quick on this.

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Joost Roeleveld wrote:
> On Saturday 09 April 2011 06:43:25 Dale wrote:
>    
>> Alan McKinnon wrote:
>>      
>>> Apparently, though unproven, at 12:48 on Saturday 09 April 2011, Dale
>>> did
>>> opine thusly:
>>> Yes.
>>>
>>> PVs, VGs, LVs all have a concept of extend|resize|reduce. What that
>>> means
>>> depends on what you are working with, but they all make the thing bigger
>>> or smaller.
>>>
>>> For a PV it means the underlying device's size changed, so the PV must
>>> change to match. Take a 500G drive, create 1 partition on it of 100G
>>> and make it a PV. Now enlarge the partition to 200G, you must extend
>>> the PV to match.
>>>
>>> A VG isn't a single thing, it's a collection of things. Extending it
>>> means to add more PVs, reducing it means to take PVs out of the VG.
>>> Hopefully you will always remember to migrate the data off a PV before
>>> removing it from a VG :-)
>>>
>>> Extend/Reduce an LV means to make the device larger/smaller. It is
>>> exactly the same thing as changing a partition size using fdisk.
>>> Obviously, you need to tweak the filesystem at the same time
>>>        
>> So, when I get me a new drive, I use pvcreate to get it ready for LVM,
>> then use vgextend to add it to the VG, then it is available for whatever
>> LV I want to extend or to make a new LV?
>>
>> I think I am catching on here.  It was just difficult for me to grasp
>> how things are layered for some reason.  Some of the pictures I found
>> helped a good bit tho.  Just helped me picture what the commands are
>> doing exactly.
>>
>> I did learn the hard way to resize the file system tho.  I forgot that
>> earlier.  Sort of had me scratching my head for a bit.  lol
>>      
> That's an easy one to miss :)
>
> You do seem to be catching on quick on this.
>
> --
> Joost
>
>    

I think I am too.  Since folks know I am disabled anyway, I went to the 
Dr the other day.  The new meds aren't perfect but it is better.  When I 
go back, he may change it to another med.  He just wanted to try this 
first.  It does sort of help me to get a better grasp on things tho.  
Sort of weird in a way.  That part is like a side effect.  :/

I'm just needing to find me a good LARGE drive to put in here.  I'm 
checking out the reviews but it just seems most have issues.  May just 
have to buy one, work the stuffing out of it with a script or something 
to see if it holds up.

I see some of the large drives spin slower, some a lot slower.  Given 
the density of the data, are they about as fast as a drive that spins at 
7200?  My main drives for my OS and the large drive I already have turn 
at 7200 rpms.  I'm just curious if that would be slower or because of 
the density of the data, it doesn't matter.  I get about 80 to 100Mb/sec 
on my current drives.  I have 3gbs/sec drives which is what my mobo 
maxes out at.  I thought about getting a 6Gb/sec just in case I upgrade 
my mobo later.

My data drive mostly has audio/video stuff but does contain pictures I 
took with my camera and some documents, mostly saved web pages or OOo 
stuff.  My 750Gb drives plays audio/video stuff just fine, even the HD 
stuff.  I just wouldn't want to get a drive that is slow enough to cause 
pauses and such.

I see newegg has 3Tb drives too.  he he he he  O_O

Thoughts?

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Thanasis]

on 04/09/2011 04:33 PM Dale wrote the following:
> <snip>
> I'm just needing to find me a good LARGE drive to put in here.  I'm
> checking out the reviews but it just seems most have issues.
> <snip>
> Thoughts?
>
I think you should be safe with WD1002FAEX, WD1502FAEX and WD2002FAEX.

Re: [gentoo-user] LVM for data drives but not the OS

[Mark Knecht]

On Sat, Apr 9, 2011 at 6:33 AM, Dale <rdalek1967@gmail.com> wrote:
<SNIP>
>
> I think I am too.  Since folks know I am disabled anyway, I went to the Dr
> the other day.  The new meds aren't perfect but it is better.  When I go
> back, he may change it to another med.  He just wanted to try this first.
>  It does sort of help me to get a better grasp on things tho.  Sort of weird
> in a way.  That part is like a side effect.  :/
>
> I'm just needing to find me a good LARGE drive to put in here.  I'm checking
> out the reviews but it just seems most have issues.  May just have to buy
> one, work the stuffing out of it with a script or something to see if it
> holds up.
>
> I see some of the large drives spin slower, some a lot slower.  Given the
> density of the data, are they about as fast as a drive that spins at 7200?
>  My main drives for my OS and the large drive I already have turn at 7200
> rpms.  I'm just curious if that would be slower or because of the density of
> the data, it doesn't matter.  I get about 80 to 100Mb/sec on my current
> drives.  I have 3gbs/sec drives which is what my mobo maxes out at.  I
> thought about getting a 6Gb/sec just in case I upgrade my mobo later.
>
> My data drive mostly has audio/video stuff but does contain pictures I took
> with my camera and some documents, mostly saved web pages or OOo stuff.  My
> 750Gb drives plays audio/video stuff just fine, even the HD stuff.  I just
> wouldn't want to get a drive that is slow enough to cause pauses and such.
>
> I see newegg has 3Tb drives too.  he he he he  O_O
>
> Thoughts?
>
> Dale

Good thread Dale. I've been busy this week so I finally read the whole
thing, start to finish, this morning. Good LVM info which I expect
I'll use one of these days myself.

Personally II think one thing you might want to consider, given your
concerns about not losing important personal data, is to investigate
RAID with the same level of focus that you are doing with LVM. Instead
of buying very large drives (3TB) you can build a large RAID6 or RAID5
out of smaller 500GB or 1TB drives. Personally my home compute server,
which runs 4 copies of Windows 7 in VMWare and Virtualbox for trading
in the futures market, is set up this way:

- Five 500GB WD RAID Edition physical drives

- /boot is just a 100MB partition on /dev/sda, but I've saved more
partition space on other drives with various kernel images should
/dev/sda fail.

- Gentoo is on a 50GB 5-drive RAID1. That's a LOT of redundancy. I can
technically lose 4 drives and the system continues to work fine. For
the OS that's essentially unkillable short of someting like a power
supply failure taking out all the drives or the MB.

- /home is on a 5-drive RAID6 using 50GB partitions. That gives me a
total of 150GB storage personally for my pictures, videos, code, etc.,
and allows 2 drives to fail without losing data.

- /VirtualMachines is on a 5-drive RAID6 using the remaining 400GB on
each drive, so that's 1.2TB with redundancy of a 2-drive loss being
protected.

I then have a few external eSATA hard drives that I use for backups.
/home to one pair, /VirtualMachines to another pair.

I think if I was to set up this system from scratch again I might
consider one large RAID6 using 450GB and putting /home in one LV and
/VirtualMachines in another. The advantage would be that over time, if
my personal needs increased, I could resize the LVs more easily than
resizing the RAIDs. (Which is also possible but beyond the scope of
this thread...)

Anyway, it's just another idea about how you can use the same hardware
in a different configuration. Five 1TB drives as a RAID6 gives you
both 3TB of storage as well as far more reliability. One 3TB drive by
itself can die and everything is gone.

Congrats on your learning experience and I hope it continues to be
successful for you.

Cheers,
Mark

Re: [gentoo-user] LVM for data drives but not the OS

[Alan McKinnon]

Apparently, though unproven, at 13:43 on Saturday 09 April 2011, Dale did 
opine thusly:

> So, when I get me a new drive, I use pvcreate to get it ready for LVM, 
> then use vgextend to add it to the VG, then it is available for whatever 
> LV I want to extend or to make a new LV?

Yup, that's really what it's all about.



LVM will decide for itself what bits of what PV to use for each LV, you should 
just let it go ahead and make it's own decisions. The man page describes 
options where you can control stuff - like striping and mirroring. I find this 
just confuses the issue though and makes stuff needlessly complex.

A much better viewpoint is you deal with your striping and performance issues 
at a lower layer - RAID - and treat LVM as something that creates a gigantic 
storage bucket where you take out how much you need and don't care where it 
is. If two drives have vastly different performance characteristics and you 
find yourself having to dictate to LVM what to do, then they really should not 
be in the same VG at all.

-- 
alan dot mckinnon at gmail dot com

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Neil Bothwick wrote:
> On Fri, 08 Apr 2011 18:36:28 -0500, Dale wrote:
>
>    
>>> A little time saver, if you have only one VG, set $LVM_VG_NAME to its
>>> name and you can leave the VG name out of any lv* commands.
>>>        
>    
>> I'll have more than one before long so may as well learn the long way.
>> Neat to know tho.  I'm hoping for about a 2Tb or maybe a 1.5Tb drive.
>> That should last me a while but I'm going to put my current 750Gb on
>> there too.
>>      
> No matter how many drives you have, I doubt you'll need more than one
> volume group.
>
>
>    

Ah, I see what you are saying now.  I may have two or three PV's, and 
several LV's but only one VG.  My bulb got a little brighter.

I could end up putting /usr, /var, and such on LVM one day.  I wouldn't 
want to go as far as having to have the initrd thingy tho.  Basically a 
minimal / with some of the other growing stuff on LVM.

Still trying to grasp making it larger while still online.  Plain 
weird.  O_O

Dale

:-) :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Neil Bothwick]

[-- Attachment #1: Type: text/plain, Size: 690 bytes --]

On Fri, 8 Apr 2011 20:38:21 +0200, Alan McKinnon wrote:

> > So when I get ready to make a file system, say ext3, then it would be
> > mkfs.ext3 /dev/mapper/<whatever>.  Then it would be ready to put
> > stuff on.  
> 
> Yup. You'll have to poke around /dev/ a bit to see how your udev does
> it today but you got the gist of it

Normally, each LV appears as /dev/vgname/lvname, which is slightly easier
to work with than /dev/mapper/vgname-lvname.

As for GUIs, they have two problems. They hide the working from you,
which is counter-productive, and all the current ones suck.


-- 
Neil Bothwick

Welcome to the world of Windows 95. Stay a while -- stay foooreveeer.

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 198 bytes --]

Re: [gentoo-user] LVM for data drives but not the OS

[Peter Humphrey]

On Thursday 07 April 2011 14:21:33 Joost Roeleveld wrote:

> Dale, this comment isn't meant as an insult. I honestly think you would be
> perfect for some QA or Testing job :)

<pedant>

QA != Testing

QA is the features of a company organisation that give it the characteristic of 
not introducing faults.

</pedant>

-- 
Rgds
Peter

Re: [gentoo-user] LVM for data drives but not the OS

[BRM]

----- Original Message ----

> From: Neil Bothwick <neil@digimed.co.uk>
> On Thu, 07 Apr 2011 05:22:41 -0500, Dale wrote:
> > I want to do it this  way because I don't trust LVM enough to put my OS 
> > on.  Just my  personal opinion on LVM.
> This doesn't make sense. Your OS can be  reinstalled in an hour or two,
> your photos etc. are  irreplaceable.
> 

Makes perfect sense to me as well.

Having installed LVM - and then removed it due to issues; namely, the fact that 
one of the hard drives died taking out the whole LVM group, leaving the OS 
unbootable, and not easily fixable. There was a thread on that (started by me) a 
while back (over a year).

So, perhaps if I had a RAID to underly so I could mirror drives under LVM for 
recovery I'd move to it again. But otherwise it is just a PITA waiting to 
happen.

Ben

Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Thursday 07 April 2011 06:20:55 BRM wrote:
> ----- Original Message ----
> 
> > From: Neil Bothwick <neil@digimed.co.uk>
> > 
> > On Thu, 07 Apr 2011 05:22:41 -0500, Dale wrote:
> > > I want to do it this  way because I don't trust LVM enough to put my
> > > OS
> > > on.  Just my  personal opinion on LVM.
> > 
> > This doesn't make sense. Your OS can be  reinstalled in an hour or two,
> > your photos etc. are  irreplaceable.
> 
> Makes perfect sense to me as well.
> 
> Having installed LVM - and then removed it due to issues; namely, the fact
> that one of the hard drives died taking out the whole LVM group, leaving
> the OS unbootable, and not easily fixable. There was a thread on that
> (started by me) a while back (over a year).
> 
> So, perhaps if I had a RAID to underly so I could mirror drives under LVM
> for recovery I'd move to it again. But otherwise it is just a PITA waiting
> to happen.
> 
> Ben

Unfortunately, any method that spreads a filesystem over multiple disks can be 
affected if one of those disks dies unless there is some mechanism in place 
that can handle the loss of a disk.
For that, RAID (with the exception of striping, eg. RAID-0) provides that.

Just out of curiousity, as I never had the need to look into this, I think 
that, in theory, it should be possible to recover data from LVs that were not 
using the failed drive. Is this assumption correct or wrong?

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[BRM]

----- Original Message ----

> From: Joost Roeleveld <joost@antarean.org>
> On Thursday 07 April 2011 06:20:55 BRM wrote:
> > ----- Original Message  ----
> > > From: Neil Bothwick <neil@digimed.co.uk>
> > > On Thu, 07 Apr 2011 05:22:41 -0500, Dale wrote:
> > > >  I want to do it this  way because I don't trust LVM enough to put  my
> > > > OS
> > > > on.  Just my  personal  opinion on LVM.
> > > 
> > > This doesn't make sense. Your OS can  be  reinstalled in an hour or two,
> > > your photos etc. are   irreplaceable.
> > 
> > Makes perfect sense to me as well.
> > 
> > Having installed LVM - and then removed it due to issues; namely, the  fact
> > that one of the hard drives died taking out the whole LVM group,  leaving
> > the OS unbootable, and not easily fixable. There was a thread on  that
> > (started by me) a while back (over a year).
> > 
> > So,  perhaps if I had a RAID to underly so I could mirror drives under LVM
> >  for recovery I'd move to it again. But otherwise it is just a PITA  waiting
> > to happen.
> > 
> > Ben
> 
> Unfortunately, any method  that spreads a filesystem over multiple disks can be 
>
> affected if one of  those disks dies unless there is some mechanism in place 
> that can handle the  loss of a disk.
> For that, RAID (with the exception of striping, eg. RAID-0)  provides that.
> 
> Just out of curiousity, as I never had the need to look  into this, I think 
> that, in theory, it should be possible to recover data  from LVs that were not 

> using the failed drive. Is this assumption correct or  wrong?
> 

If you have the LV configuration information, then yes. Since I managed to find 
the configuration information, I was able to remove the affected PVs from the 
VG, and get it back up.
I might still have it running, but I'll back it out on the next rebuild - or if 
I have a drive large enough to do so with in the future. I was wanting to use 
LVM as a bit of a software RAID, but never quite got
that far in the configuration before it failed. It does do a good job at what 
it's designed for, but I would not trust the OS to it either since the LVM 
configuration is very important to keep around.

If not, good luck as far as I can tell.

Ben

Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Thursday 07 April 2011 06:52:26 BRM wrote:
> ----- Original Message ----
> 
> > From: Joost Roeleveld <joost@antarean.org>
> > 
> > On Thursday 07 April 2011 06:20:55 BRM wrote:
> > > ----- Original Message  ----
> > > 
> > > > From: Neil Bothwick <neil@digimed.co.uk>
> > > > 
> > > > On Thu, 07 Apr 2011 05:22:41 -0500, Dale wrote:
> > > > >  I want to do it this  way because I don't trust LVM enough
> > > > >  to put  my
> > > > > 
> > > > > OS
> > > > > on.  Just my  personal  opinion on LVM.
> > > > 
> > > > This doesn't make sense. Your OS can  be  reinstalled in an hour
> > > > or two, your photos etc. are   irreplaceable.
> > > 
> > > Makes perfect sense to me as well.
> > > 
> > > Having installed LVM - and then removed it due to issues; namely,
> > > the  fact that one of the hard drives died taking out the whole LVM
> > > group,  leaving the OS unbootable, and not easily fixable. There
> > > was a thread on  that (started by me) a while back (over a year).
> > > 
> > > So,  perhaps if I had a RAID to underly so I could mirror drives
> > > under LVM
> > > 
> > >  for recovery I'd move to it again. But otherwise it is just a PITA
> > >   waiting
> > > 
> > > to happen.
> > > 
> > > Ben
> > 
> > Unfortunately, any method  that spreads a filesystem over multiple disks
> > can be
> > 
> > affected if one of  those disks dies unless there is some mechanism in
> > place that can handle the  loss of a disk.
> > For that, RAID (with the exception of striping, eg. RAID-0)  provides
> > that.
> > 
> > Just out of curiousity, as I never had the need to look  into this, I
> > think that, in theory, it should be possible to recover data  from LVs
> > that were not
> > 
> > using the failed drive. Is this assumption correct or  wrong?
> 
> If you have the LV configuration information, then yes. Since I managed to
> find the configuration information, I was able to remove the affected PVs
> from the VG, and get it back up.
> I might still have it running, but I'll back it out on the next rebuild - or
> if I have a drive large enough to do so with in the future. I was wanting
> to use LVM as a bit of a software RAID, but never quite got
> that far in the configuration before it failed. It does do a good job at
> what it's designed for, but I would not trust the OS to it either since the
> LVM configuration is very important to keep around.
> 
> If not, good luck as far as I can tell.
> 
> Ben

LVM isn't actually RAID. Not in the sense that one gets redundancy. If you 
consider it to be a flexible partitioning method, that can span multiple disks, 
then yes.
But when spanning multiple disks, it will simply act like JBOD or RAID0. 
Neither protects someone from a single disk failure.

On critical systems, I tend to use:
DISK <-> RAID <-> LVM <-> Filesystem

The disks are as reliable as Google says they are. They fail or they don't.
RAID protects against single disk-failure
LVM makes the partitioning flexible
Filesystems are picked depending on what I use the partition for

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[BRM]

----- Original Message ----

> From: Joost Roeleveld <joost@antarean.org>
> On Thursday 07 April 2011 06:52:26 BRM wrote:
> > ----- Original Message  ----
> > 
> > > From: Joost Roeleveld <joost@antarean.org>
> > > 
> > > On Thursday 07 April 2011 06:20:55 BRM wrote:
> > > >  ----- Original Message  ----
> > > > 
> > > > >  From: Neil Bothwick <neil@digimed.co.uk>
> > > >  > 
> > > > > On Thu, 07 Apr 2011 05:22:41 -0500, Dale  wrote:
> > > > > >  I want to do it this  way because  I don't trust LVM enough
> > > > > >  to put   my
> > > > > > 
> > > > > > OS
> > > >  > > on.  Just my  personal  opinion on LVM.
> > >  > > 
> > > > > This doesn't make sense. Your OS can   be  reinstalled in an hour
> > > > > or two, your photos etc.  are   irreplaceable.
> > > > 
> > > > Makes perfect  sense to me as well.
> > > > 
> > > > Having installed LVM -  and then removed it due to issues; namely,
> > > > the  fact that  one of the hard drives died taking out the whole LVM
> > > >  group,  leaving the OS unbootable, and not easily fixable. There
> >  > > was a thread on  that (started by me) a while back (over a  year).
> > > > 
> > > > So,  perhaps if I had a RAID to  underly so I could mirror drives
> > > > under LVM
> > > > 
> > > >  for recovery I'd move to it again. But otherwise it is  just a PITA
> > > >   waiting
> > > > 
> > >  > to happen.
> > > > 
> > > > Ben
> > > 
> >  > Unfortunately, any method  that spreads a filesystem over multiple  disks
> > > can be
> > > 
> > > affected if one of   those disks dies unless there is some mechanism in
> > > place that can  handle the  loss of a disk.
> > > For that, RAID (with the exception  of striping, eg. RAID-0)  provides
> > > that.
> > > 
> >  > Just out of curiousity, as I never had the need to look  into this,  I
> > > think that, in theory, it should be possible to recover  data  from LVs
> > > that were not
> > > 
> > > using  the failed drive. Is this assumption correct or  wrong?
> > 
> > If  you have the LV configuration information, then yes. Since I managed to
> >  find the configuration information, I was able to remove the affected  PVs
> > from the VG, and get it back up.
> > I might still have it  running, but I'll back it out on the next rebuild - 
or
> > if I have a drive  large enough to do so with in the future. I was wanting
> > to use LVM as a  bit of a software RAID, but never quite got
> > that far in the  configuration before it failed. It does do a good job at
> > what it's  designed for, but I would not trust the OS to it either since the
> > LVM  configuration is very important to keep around.
> > 
> > If not, good  luck as far as I can tell.
> > 
> > Ben
> 
> LVM isn't actually RAID.  Not in the sense that one gets redundancy. If you 
> consider it to be a  flexible partitioning method, that can span multiple 
>disks, 
>
> then yes.
> But  when spanning multiple disks, it will simply act like JBOD or RAID0. 
> Neither  protects someone from a single disk failure.
> 
> On critical systems, I tend  to use:
> DISK <-> RAID <-> LVM <-> Filesystem
> 
> The  disks are as reliable as Google says they are. They fail or they don't.
> RAID  protects against single disk-failure
> LVM makes the partitioning  flexible
> Filesystems are picked depending on what I use the partition  for
> 

The attraction to LVM for me was that from what I could tell it supported and 
implemented a software-RAID
so that I could help protect from disk-failure. I never got around to 
configuring that side of it, but that was my goal.
Or are you saying I was misunderstanding and LVM _does not_ contain 
software-RAID support?

Ben

Re: [gentoo-user] LVM for data drives but not the OS

[J. Roeleveld]

On Thu, April 7, 2011 7:31 pm, BRM wrote:
> ----- Original Message ----
>
>> From: Joost Roeleveld <joost@antarean.org>
>> On Thursday 07 April 2011 06:52:26 BRM wrote:
>> > ----- Original Message  ----
>> >
>> > > From: Joost Roeleveld <joost@antarean.org>
>> > >
>> > > On Thursday 07 April 2011 06:20:55 BRM wrote:
>> > > >  ----- Original Message  ----
>> > > >
>> > > > >  From: Neil Bothwick <neil@digimed.co.uk>
>> > > >  >
>> > > > > On Thu, 07 Apr 2011 05:22:41 -0500, Dale  wrote:
>> > > > > >  I want to do it this  way because  I don't trust LVM enough
>> > > > > >  to put   my
>> > > > > >
>> > > > > > OS
>> > > >  > > on.  Just my  personal  opinion on LVM.
>> > >  > >
>> > > > > This doesn't make sense. Your OS can   be  reinstalled in an
>> hour
>> > > > > or two, your photos etc.  are   irreplaceable.
>> > > >
>> > > > Makes perfect  sense to me as well.
>> > > >
>> > > > Having installed LVM -  and then removed it due to issues; namely,
>> > > > the  fact that  one of the hard drives died taking out the whole
>> LVM
>> > > >  group,  leaving the OS unbootable, and not easily fixable. There
>> >  > > was a thread on  that (started by me) a while back (over a
>> year).
>> > > >
>> > > > So,  perhaps if I had a RAID to  underly so I could mirror drives
>> > > > under LVM
>> > > >
>> > > >  for recovery I'd move to it again. But otherwise it is  just a
>> PITA
>> > > >   waiting
>> > > >
>> > >  > to happen.
>> > > >
>> > > > Ben
>> > >
>> >  > Unfortunately, any method  that spreads a filesystem over multiple
>> disks
>> > > can be
>> > >
>> > > affected if one of   those disks dies unless there is some mechanism
>> in
>> > > place that can  handle the  loss of a disk.
>> > > For that, RAID (with the exception  of striping, eg. RAID-0)
>> provides
>> > > that.
>> > >
>> >  > Just out of curiousity, as I never had the need to look  into this,
>>  I
>> > > think that, in theory, it should be possible to recover  data  from
>> LVs
>> > > that were not
>> > >
>> > > using  the failed drive. Is this assumption correct or  wrong?
>> >
>> > If  you have the LV configuration information, then yes. Since I
>> managed to
>> >  find the configuration information, I was able to remove the affected
>>  PVs
>> > from the VG, and get it back up.
>> > I might still have it  running, but I'll back it out on the next
>> rebuild -
> or
>> > if I have a drive  large enough to do so with in the future. I was
>> wanting
>> > to use LVM as a  bit of a software RAID, but never quite got
>> > that far in the  configuration before it failed. It does do a good job
>> at
>> > what it's  designed for, but I would not trust the OS to it either
>> since the
>> > LVM  configuration is very important to keep around.
>> >
>> > If not, good  luck as far as I can tell.
>> >
>> > Ben
>>
>> LVM isn't actually RAID.  Not in the sense that one gets redundancy. If
>> you
>> consider it to be a  flexible partitioning method, that can span
>> multiple
>>disks,
>>
>> then yes.
>> But  when spanning multiple disks, it will simply act like JBOD or
>> RAID0.
>> Neither  protects someone from a single disk failure.
>>
>> On critical systems, I tend  to use:
>> DISK <-> RAID <-> LVM <-> Filesystem
>>
>> The  disks are as reliable as Google says they are. They fail or they
>> don't.
>> RAID  protects against single disk-failure
>> LVM makes the partitioning  flexible
>> Filesystems are picked depending on what I use the partition  for
>>
>
> The attraction to LVM for me was that from what I could tell it supported
> and
> implemented a software-RAID
> so that I could help protect from disk-failure. I never got around to
> configuring that side of it, but that was my goal.
> Or are you saying I was misunderstanding and LVM _does not_ contain
> software-RAID support?

Unless I am mistaken, LVM does not provide redundancy. It provides
disk-spanning (JBOD) and basic striping (RAID-0).

For redundancy, I would use a proper RAID (either hardware or software).
On top of this, you can then decide to have a single filesystem, LVM or
even partition this.

I think the confusion might have come from the fact that both LVM and
Linux Software Raid use the "Device Mapper" interface in the kernel config
and they are in the same part.

Also, part of the problem is that striping is also called RAID-0. That, to
people who don't fully understand it yet, makes it sound like it is a
RAID.
It actually isn't as it doesn't provide any redundancy.

I do hope you didn't loose too much important data when you had this issue.

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[BRM]

----- Original Message ----

> From: J. Roeleveld <joost@antarean.org>
> On Thu, April 7, 2011 7:31 pm, BRM wrote:
> > The attraction to LVM  for me was that from what I could tell it supported
> > and
> >  implemented a software-RAID
> > so that I could help protect from  disk-failure. I never got around to
> > configuring that side of it, but  that was my goal.
> > Or are you saying I was misunderstanding and LVM _does  not_ contain
> > software-RAID support?
> 
> Unless I am mistaken, LVM  does not provide redundancy. It provides
> disk-spanning (JBOD) and basic  striping (RAID-0).
> 
> For redundancy, I would use a proper RAID (either  hardware or software).
> On top of this, you can then decide to have a single  filesystem, LVM or
> even partition this.
> 
> I think the confusion might  have come from the fact that both LVM and
> Linux Software Raid use the "Device  Mapper" interface in the kernel config
> and they are in the same  part.
> 
> Also, part of the problem is that striping is also called RAID-0.  That, to
> people who don't fully understand it yet, makes it sound like it is  a
> RAID.
> It actually isn't as it doesn't provide any redundancy.

I think the issue comes from the fact that LVM2 supports Mirroring without an 
underlying RAID controller:

http://tinyurl.com/3woh2d7
http://en.wikipedia.org/wiki/Logical_Volume_Manager_%28Linux%29
http://www.gossamer-threads.com/lists/gentoo/performance/59776

Which would be a redundancy.

> 
> I  do hope you didn't loose too much important data when you had this  issue.
> 

No, I didn't loose any important data (fortunately). If I did, I would have paid 
for the drive to be recovered; it was mostly portage, var/tmp, some extra 
sandbox stuff, kind of things.

Ben

Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Thursday 07 April 2011 11:35:42 BRM wrote:
> ----- Original Message ----
> 
> > From: J. Roeleveld <joost@antarean.org>
> 
> I think the issue comes from the fact that LVM2 supports Mirroring without
> an underlying RAID controller:
> 
> http://tinyurl.com/3woh2d7
> http://en.wikipedia.org/wiki/Logical_Volume_Manager_%28Linux%29
> http://www.gossamer-threads.com/lists/gentoo/performance/59776
> 
> Which would be a redundancy.

Ok, I wasn't aware of that bit.
From the first hit in the google-list, I do think that LVM-mirror isn't really 
ready. Especially as the read-performance is less then using software raid.

I don't find mdadm difficult to use though. It's a vast improvement over the old 
raidtools.

> > I  do hope you didn't loose too much important data when you had this 
> > issue.
> 
> No, I didn't loose any important data (fortunately). If I did, I would have
> paid for the drive to be recovered; it was mostly portage, var/tmp, some
> extra sandbox stuff, kind of things.

Glad to hear that.

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

I been reading this howto:

http://www.tldp.org/HOWTO/LVM-HOWTO/index.html

It hasn't been updated in several years now.  Should I be reading this 
or is it up to date enough that I wont end up confused because of 
changes that have occurred since that howto has been updated?   I don't 
want to learn something just to find out that there has been changes and 
then get my brain turned to soup.

Little light bulb here.  physical volume is the same as a physical 
drive?  If I understand it correctly, it is the whole thing unpartitioned.

I'm hoping for some nice pictures before to long to help explain this 
some more.  lol

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Neil Bothwick]

[-- Attachment #1: Type: text/plain, Size: 370 bytes --]

On Fri, 08 Apr 2011 05:42:59 -0500, Dale wrote:

> Little light bulb here.  physical volume is the same as a physical 
> drive?  If I understand it correctly, it is the whole thing
> unpartitioned.

No. A physical volume is an area of disk. It can be the whole disk but it
more usually a partition.


-- 
Neil Bothwick

Top Oxymorons Number 18: Taped live

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 198 bytes --]

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Neil Bothwick wrote:
> On Fri, 08 Apr 2011 05:42:59 -0500, Dale wrote:
>
>    
>> Little light bulb here.  physical volume is the same as a physical
>> drive?  If I understand it correctly, it is the whole thing
>> unpartitioned.
>>      
> No. A physical volume is an area of disk. It can be the whole disk but it
> more usually a partition.
>
>    

Ooooh.  Still some progress tho.  lol  So, if I was going to use LVM, I 
create a partition first, either whole drive or part of it then use LVM 
on that?  Then comes in the rest of the stuff that I am still trying to 
get a grip on.

This reminds me of catching a catfish.  It's slimy and hard to get a 
grip on.  lol

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Alan McKinnon]

On Friday 08 April 2011 15:40:18 Dale wrote:
> Neil Bothwick wrote:
> > On Fri, 08 Apr 2011 05:42:59 -0500, Dale wrote:
> >> Little light bulb here.  physical volume is the same as a physical
> >> drive?  If I understand it correctly, it is the whole thing
> >> unpartitioned.
> > 
> > No. A physical volume is an area of disk. It can be the whole disk but it
> > more usually a partition.
> 
> Ooooh.  Still some progress tho.  lol  So, if I was going to use LVM, I
> create a partition first, either whole drive or part of it then use LVM
> on that?  Then comes in the rest of the stuff that I am still trying to
> get a grip on.

Yes.

Here's the sequence:

1. Start with some sort of storage device (disk, partition, whatever - it must 
just be a block device)

2. Run pvcreate on it. This is like making swapspace - it adds a signature to 
the beginning of the block device so that LVM knows it can use the device

3. Add the pv to a volume group (vg). A vg is a collection of one or more 
pv's, they are so that you can build big vgs and create volumes larger than 
any one disk. On desktop with one drive or one RAID device, then vg often only 
has 1 pv in it

4. Allocate space from the vg. This is a logical volume, it is a block device 
just like any other and as far as the kernel and you are concerned you use it. 
mkfs it and mount it just like any other block device.

====

Each of these elements (pv, vg, lv) can be added to, created, extended, 
reduced and the command systax is much the same for each. What that means 
exactly depends on what the thing is:

PV: creating it starts it from scratch, the LVM data on it is gone. You only 
extend/reduce a PV if you changed the size of the underlying partition so that 
LVM know it's true size.

VG: You don't really create a VG as such (it's a collection of things, not a 
single thing). Creating it means adding the first PV to the VG. Extending and 
reducing a VG means adding and removing PVs from the collection. When you 
reduce a VG, it's an excellent idea to have migrated all the data on the PV 
away first :-)

LV: Make the LV larger or smaller. This is conceptually exactly the same as 
modifying a regular partition with fdisk, and you must take the same 
precautions:

  Extend: Make the LV bigger then grow the fs on it to use all the space
  Reduce: Shrink the fs on it then reduce the LV to the same size



It's all very simple and logical really. It you grok what create/extend/reduce 
and so on means for each element then you won't go wrong. People get confused 
by LVM because tutorials on it, Red Hat training materials[1] and GUI tools 
try very hard to fudge the concept, hide the bits and present it like the 
partition, PV, VG, LV and filesystem on it and somehow all the same thing. 
Which is completely not true of course.

[1] Especially Red Hat training materials. These caused more confusion about 
it than anything else I have ever seen. Including Gnome tools. And that's 
saying something.





-- 
alan dot mckinnon at gmail dot com

Re: [gentoo-user] LVM for data drives but not the OS

[Mark Knecht]

On Fri, Apr 8, 2011 at 6:40 AM, Dale <rdalek1967@gmail.com> wrote:
> Neil Bothwick wrote:
>>
>> On Fri, 08 Apr 2011 05:42:59 -0500, Dale wrote:
>>
>>
>>>
>>> Little light bulb here.  physical volume is the same as a physical
>>> drive?  If I understand it correctly, it is the whole thing
>>> unpartitioned.
>>>
>>
>> No. A physical volume is an area of disk. It can be the whole disk but it
>> more usually a partition.
>>
>>
>
> Ooooh.  Still some progress tho.  lol  So, if I was going to use LVM, I
> create a partition first, either whole drive or part of it then use LVM on
> that?  Then comes in the rest of the stuff that I am still trying to get a
> grip on.
>
> This reminds me of catching a catfish.  It's slimy and hard to get a grip
> on.  lol
>
> Dale

Dale,
   As for the 'whole disk' hint, I think what Neil means is that the
drive doesn't need to be partitioned at all. I.e., instead of

mke2fs -j /dev/sda3

think

mke2fs -j /dev/sda

- Mark

Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Friday 08 April 2011 08:40:18 Dale wrote:
> Neil Bothwick wrote:
> > On Fri, 08 Apr 2011 05:42:59 -0500, Dale wrote:
> >> Little light bulb here.  physical volume is the same as a physical
> >> drive?  If I understand it correctly, it is the whole thing
> >> unpartitioned.
> > 
> > No. A physical volume is an area of disk. It can be the whole disk but
> > it
> > more usually a partition.
> 
> Ooooh.  Still some progress tho.  lol  So, if I was going to use LVM, I
> create a partition first, either whole drive or part of it then use LVM
> on that?

Yes. correct. Don't forget to set the partition type to "Linux LVM" (8e).

> Then comes in the rest of the stuff that I am still trying to
> get a grip on.

I'm confident you'll get there.

> This reminds me of catching a catfish.  It's slimy and hard to get a
> grip on.  lol

So are most fish, I believe...
Do you fish with your bare hands?

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Joost Roeleveld wrote:
> On Friday 08 April 2011 08:40:18 Dale wrote:
>    
>> Neil Bothwick wrote:
>>      
>>> On Fri, 08 Apr 2011 05:42:59 -0500, Dale wrote:
>>>        
>>>> Little light bulb here.  physical volume is the same as a physical
>>>> drive?  If I understand it correctly, it is the whole thing
>>>> unpartitioned.
>>>>          
>>> No. A physical volume is an area of disk. It can be the whole disk but
>>> it
>>> more usually a partition.
>>>        
>> Ooooh.  Still some progress tho.  lol  So, if I was going to use LVM, I
>> create a partition first, either whole drive or part of it then use LVM
>> on that?
>>      
> Yes. correct. Don't forget to set the partition type to "Linux LVM" (8e).
>    

That would be done in cfdisk I presume.  I think that is where I saw that.

>    
>> Then comes in the rest of the stuff that I am still trying to
>> get a grip on.
>>      
> I'm confident you'll get there.
>    

One of these days.

>    
>> This reminds me of catching a catfish.  It's slimy and hard to get a
>> grip on.  lol
>>      
> So are most fish, I believe...
> Do you fish with your bare hands?
>
> --
> Joost
>
>    

I love to fish.  I have issues with stress which is why I try to avoid 
it when I can so fishing is good for me plus I like to eat fish.  I fish 
with a rod and a hook but they usually don't like when you start pulling 
the hook out.  He tends to want to get away.  That's where the slimy 
part comes in.  I'm not sure where you are from but in some parts of the 
USA, some bright people do fish with their hands, usually very large 
catfish too.  I saw it on TV and I wish I could catch one of those, even 
if I would need a new rod.  A fish that size would likely break my rod 
unless I was using the deep sea fishing rod.  Those fish weigh 30 lbs 
and some LOTS more.  It's like pulling a teenager out of the water.  
O_O  They are big.

OK.  Back to LVM.  lol

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Friday 08 April 2011 09:45:48 Dale wrote:
> Joost Roeleveld wrote:
> > On Friday 08 April 2011 08:40:18 Dale wrote:
> >> Neil Bothwick wrote:
> >>> On Fri, 08 Apr 2011 05:42:59 -0500, Dale wrote:
> > Yes. correct. Don't forget to set the partition type to "Linux LVM"
> > (8e).
> 
> That would be done in cfdisk I presume.  I think that is where I saw that.

Or in fdisk. Basically any decent partitioning tool can do it.

> >> Then comes in the rest of the stuff that I am still trying to
> >> get a grip on.
> > 
> > I'm confident you'll get there.
> 
> One of these days.

:)

> >> This reminds me of catching a catfish.  It's slimy and hard to get a
> >> grip on.  lol
> > 
> > So are most fish, I believe...
> > Do you fish with your bare hands?
> > 
> > --
> > Joost
> 
> I love to fish.  I have issues with stress which is why I try to avoid
> it when I can so fishing is good for me plus I like to eat fish.  I fish
> with a rod and a hook but they usually don't like when you start pulling
> the hook out.

Ok...
Only time I ever went fishing was in some fishing farm in France.
The fish there were quite good at eating the bait of the hooks. It ended up 
being a timing contest:
- Bait on hook
- Hook in water for less then a second
- Pull out hook

If you timed it right, the fish would be hooked.
Too quick, and fish wouldn't bite.
Too slow, and fish would be gone, with bait....

> He tends to want to get away.  That's where the slimy
> part comes in.  I'm not sure where you are from but in some parts of the
> USA, some bright people do fish with their hands, usually very large
> catfish too.  I saw it on TV and I wish I could catch one of those, even
> if I would need a new rod.  A fish that size would likely break my rod
> unless I was using the deep sea fishing rod.  Those fish weigh 30 lbs
> and some LOTS more.  It's like pulling a teenager out of the water.
> O_O  They are big.

That's a small teenager then. Only 30lbs (less then 25 kilos) :)

FYI: I'm in the Netherlands, Europe and looking forward to the weekend, hope 
the weather stays like this (sunny, clear sky, hardly any wind)

> OK.  Back to LVM.  lol

Oki...

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[Dale]

Joost Roeleveld wrote:
> On Friday 08 April 2011 09:45:48 Dale wrote:
>    
>> He tends to want to get away.  That's where the slimy
>> part comes in.  I'm not sure where you are from but in some parts of the
>> USA, some bright people do fish with their hands, usually very large
>> catfish too.  I saw it on TV and I wish I could catch one of those, even
>> if I would need a new rod.  A fish that size would likely break my rod
>> unless I was using the deep sea fishing rod.  Those fish weigh 30 lbs
>> and some LOTS more.  It's like pulling a teenager out of the water.
>> O_O  They are big.
>>      
> That's a small teenager then. Only 30lbs (less then 25 kilos) :)
>
> FYI: I'm in the Netherlands, Europe and looking forward to the weekend, hope
> the weather stays like this (sunny, clear sky, hardly any wind)
>
>    
>> OK.  Back to LVM.  lol
>>      
> Oki...
>
> --
> Joost
>
>    

The part about the teenager was in reference to the LOTS more.  They 
have caught fish that was close to 100 lbs.  I have a friend that even 
where we are has caught fish over 50 or 60 lbs.  To me tho, they don't 
taste good.

We have a fish called shad here.  They love to clean the hook too.  They 
have learned to come in from the side of the hook and they don't get 
caught.  That's where a small treble hook comes in tho.  It doesn't have 
sides.  lol   The shads are small but they make good bait.  Never heard 
of anybody eating them tho.  They are pretty small.

Well, gas is going up.  Going to go fill up my car and a couple jugs.  
Already got my 55 gallon drum full.  See, I ain't stupid.  :-p

Dale

:-)  :-)

Re: [gentoo-user] LVM for data drives but not the OS

[Joost Roeleveld]

On Friday 08 April 2011 05:42:59 Dale wrote:
> I been reading this howto:
> 
> http://www.tldp.org/HOWTO/LVM-HOWTO/index.html
> 
> It hasn't been updated in several years now.  Should I be reading this
> or is it up to date enough that I wont end up confused because of
> changes that have occurred since that howto has been updated?   I don't
> want to learn something just to find out that there has been changes and
> then get my brain turned to soup.

Not sure about the commands there.
The basic theory is, from a quick glance, still valid.

That it still mentions LVM1 isn't usefull for you as you'll automatically be 
using LVM2. (yes, new version came out sometimes in 2.6.x :) )

As for more current howtos:
https://wiki.archlinux.org/index.php/LVM 
http://www.gentoo.org/doc/en/lvm2.xml

And via a blog posting ( http://www.vm-aware.com/2008/08/how-to-linux-lvm/ ) I 
found 2 more:
http://www.ntlug.org/Articles/LVM
http://www.howtoforge.com/linux_lvm

> Little light bulb here.  physical volume is the same as a physical
> drive?  If I understand it correctly, it is the whole thing unpartitioned.

Eerh... Nearly there :)
Most people use partitions on a physical drive for the physical volumes.

> I'm hoping for some nice pictures before to long to help explain this
> some more.  lol

You ask, wikipedia delivers:
http://en.wikipedia.org/wiki/Logical_Volume_Manager_%28Linux%29

--
Joost

Re: [gentoo-user] LVM for data drives but not the OS

[Alex Schuster]

Dale writes:

> Quick question about LVM.  I have a 750Gb drive that has miscellaneous
> stuff on it.  Stuff likes videos, music, pictures, ISO files and a few
> other things.  It's not full yet but it is working on it.  I have my OS
> on sda.  The large drive is on sdc.  If I buy another drive it should be
> sdd.  I think this is possible from what I have read but want to make
> sure.  Could I put sdc and sdd on LVM but the OS remain as it is with
> LVM not involved at all?  Basically, my OS stays just like it is and is
> not touched my LVM at all but the two larger drives are managed by LVM.
> 
> I want to do it this way because I don't trust LVM enough to put my OS
> on.  Just my personal opinion on LVM.

# create some partitions, or a single one. I prefer to have multiple ones, 
just in case I want to put other stuff there, like another OS.
cfdisk /dev/sdd

# create physical volumes (assuming you have /dev/sdd5 to /dev/sdd8)
pvcreate /dev/sdd[5678]

# create volume group 'stuff', using all those partitions
vgcreate stuff /dev/sdd[5678]

# create logical volumes. You probably will only have a single one, but 
here's how you would do this if you want three.
lvcreate -L 300G -n music    stuff
lvcreate -L 100G -n pictures stuff
lvcreate -L 100G -n other    stuff

# create file systems
for fs in music pictures other
do
	mke2fs -j -m 1 -L $fs /dev/stuff/$fs
done

> If there is a better solution to link two large drives, I'm open to
> those ideas as well.  LVM is all I can think of is why I mention it.

RAID would be another solution.
Beware, when one drive fails, all data can be lost.

# mount the filesystems, and move stuff from sdc to them

# call cfdisk and partition sdc (if you like)

# create physical volumes:
pvcreate /dev/sdc*

# extend volume group
vgextend stuff /dev/sdc*

# want to enlarge file systems?
lvresize -L 1000G /dev/stuff/other
resize2fs /dev/stuff/other

Use pvscan, lvscan and vgscan to check what physical/logical volumes and 
volume groups you have. {pv,lv,vg}dispklay  give more verbose information.

You might want to have more than one volume group. Maybe one for not so 
important data, that spans over two disks, and one or two that reside on a 
single drive only. So in case one drive fails, you do not lose too much 
data. What about a volume group that stores backups of each file system on 
sda?

	Wonko

Re: [gentoo-user] LVM for data drives but not the OS

[Mark Shields]

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On Thu, Apr 7, 2011 at 5:22 AM, Dale <rdalek1967@gmail.com> wrote:

> Hi,
>
> Quick question about LVM.  I have a 750Gb drive that has miscellaneous
> stuff on it.  Stuff likes videos, music, pictures, ISO files and a few other
> things.  It's not full yet but it is working on it.  I have my OS on sda.
>  The large drive is on sdc.  If I buy another drive it should be sdd.  I
> think this is possible from what I have read but want to make sure.  Could I
> put sdc and sdd on LVM but the OS remain as it is with LVM not involved at
> all?  Basically, my OS stays just like it is and is not touched my LVM at
> all but the two larger drives are managed by LVM.
>
> I want to do it this way because I don't trust LVM enough to put my OS on.
>  Just my personal opinion on LVM.
>
> If there is a better solution to link two large drives, I'm open to those
> ideas as well.  LVM is all I can think of is why I mention it.
>
> Thanks.
>
> Dale
>
> :-)  :-)
>
>
I know I'm late to the game with a reply, but a couple of months ago, I
setup a data box running Gentoo in the following configuration:

OS drive:  250 GB PATA LVM2
data drives:  2 x WD Caviar Black 3 TB, raid1, LVM2

Had to partition those drives using parted, though.

If that setup works fine -- and it does -- you'll have no issues.

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