Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[J. Roeleveld]

On Thu, March 24, 2011 12:30 pm, Volker Armin Hemmann wrote:
> On Thursday 24 March 2011 08:49:52 J. Roeleveld wrote:
>> On Wed, March 23, 2011 5:43 pm, Volker Armin Hemmann wrote:
>> > md raid devices can do barriers. Don't know about lvm. But lvm is such
>> a
>> > can
>> > of worms I am surprised people still recommend it.
>>
>> What is wrong with LVM?
>> I've been using it successfully without any issues for years now.
>> It does what it says on the box.
>
> it is another layer that can go wrong. Why take the risk? There
> are enough cases of breakage after upgrades - and besides snapshots... is
> the
> amount of additional code running really worth it? Especially with bind
> mounting?

There are always things that can go wrong and I agree, adding additional
layers can increase the risk.
However, the benefits of easily and quickly changing the size of
partitions and creating snapshots for the use of backups are a big enough
benefit to off-set the risk.

Bind-mounting is ok, if you use a single filesystem for everything. I have
partitions that are filled with thousands of small files and partitions
filled with files are are, on average, at 1GB in size.
I haven't found a filesystem yet that successfully handles both of these
with identical performance.
When I first tested performance I found that a simple "ls" in a partition
would appear to just hang. This caused performance issues with my
IMAP-server.
I switched to a filesystem that better handles large amounts of small
files and performance increased significantly.

The way I do backups is that I stop the services, create snapshots and
then restart the services.
I then have plenty of time to backup the snapshot.
If I were to do this differently, I'd end up having a downtime for over an
hour just for a backup.
Now, it's barely a minute of downtime.

That, to me, is a very big bonus.

--
Joost

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Dale]

J. Roeleveld wrote:
> On Thu, March 24, 2011 12:30 pm, Volker Armin Hemmann wrote:
>    
>> On Thursday 24 March 2011 08:49:52 J. Roeleveld wrote:
>>      
>>> On Wed, March 23, 2011 5:43 pm, Volker Armin Hemmann wrote:
>>>        
>>>> md raid devices can do barriers. Don't know about lvm. But lvm is such
>>>>          
>>> a
>>>        
>>>> can
>>>> of worms I am surprised people still recommend it.
>>>>          
>>> What is wrong with LVM?
>>> I've been using it successfully without any issues for years now.
>>> It does what it says on the box.
>>>        
>> it is another layer that can go wrong. Why take the risk? There
>> are enough cases of breakage after upgrades - and besides snapshots... is
>> the
>> amount of additional code running really worth it? Especially with bind
>> mounting?
>>      
> There are always things that can go wrong and I agree, adding additional
> layers can increase the risk.
> However, the benefits of easily and quickly changing the size of
> partitions and creating snapshots for the use of backups are a big enough
> benefit to off-set the risk.
>
> Bind-mounting is ok, if you use a single filesystem for everything. I have
> partitions that are filled with thousands of small files and partitions
> filled with files are are, on average, at 1GB in size.
> I haven't found a filesystem yet that successfully handles both of these
> with identical performance.
> When I first tested performance I found that a simple "ls" in a partition
> would appear to just hang. This caused performance issues with my
> IMAP-server.
> I switched to a filesystem that better handles large amounts of small
> files and performance increased significantly.
>
> The way I do backups is that I stop the services, create snapshots and
> then restart the services.
> I then have plenty of time to backup the snapshot.
> If I were to do this differently, I'd end up having a downtime for over an
> hour just for a backup.
> Now, it's barely a minute of downtime.
>
> That, to me, is a very big bonus.
>
> --
> Joost
>
>    

I have never used LVM but when it messes up after a upgrade, as has 
happened to many others, see if you say the same thing.  I hope your 
backups are good and they can restore.

Dale

:-)  :-)

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[kashani]

On 3/24/2011 10:19 AM, Dale wrote:
>
> I have never used LVM but when it messes up after a upgrade, as has
> happened to many others, see if you say the same thing. I hope your
> backups are good and they can restore.
>
> Dale

	Meh, boot a liveCD and fix it which took all of 15 minutes. I don't see 
that as a failing of LVM, but of Gentoo for lack of another culprit. You 
can only roll your OS forward in so many ways before you have to do a 
little offline plumbing. May as well complain that you had to shutdown 
your machine to put in more RAM.

kashani

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Dale]

kashani wrote:
> On 3/24/2011 10:19 AM, Dale wrote:
>>
>> I have never used LVM but when it messes up after a upgrade, as has
>> happened to many others, see if you say the same thing. I hope your
>> backups are good and they can restore.
>>
>> Dale
>
>     Meh, boot a liveCD and fix it which took all of 15 minutes. I 
> don't see that as a failing of LVM, but of Gentoo for lack of another 
> culprit. You can only roll your OS forward in so many ways before you 
> have to do a little offline plumbing. May as well complain that you 
> had to shutdown your machine to put in more RAM.
>
> kashani
>
>

I researched using LVM a good while back.  The reason I didn't was what 
I posted.  It is prone to problems that are difficult if not impossible 
to correct.  I may not have data that is worth much but I don't want to 
loose it either way.

People that have read these posts can't plead ignorance.

Good luck.

Dale

:-)  :-)

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Bill Longman]

On 03/24/2011 11:17 AM, Dale wrote:
> kashani wrote:
>> On 3/24/2011 10:19 AM, Dale wrote:
>>>
>>> I have never used LVM but when it messes up after a upgrade, as has
>>> happened to many others, see if you say the same thing. I hope your
>>> backups are good and they can restore.
>>>
>>> Dale
>>
>>     Meh, boot a liveCD and fix it which took all of 15 minutes. I
>> don't see that as a failing of LVM, but of Gentoo for lack of another
>> culprit. You can only roll your OS forward in so many ways before you
>> have to do a little offline plumbing. May as well complain that you
>> had to shutdown your machine to put in more RAM.
>>
>> kashani
>>
>>
> 
> I researched using LVM a good while back.  The reason I didn't was what
> I posted.  It is prone to problems that are difficult if not impossible
> to correct.  I may not have data that is worth much but I don't want to
> loose it either way.
> 
> People that have read these posts can't plead ignorance.

Yet you, who "have never used LVM" *can* plead knowledge?
Uh....something's really wrong in this formula.

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Alan McKinnon]

On Thursday 24 March 2011 12:19:39 Dale wrote:

> I have never used LVM but when it messes up after a upgrade, as has
> happened to many others, see if you say the same thing.  I hope your
> backups are good and they can restore.

What is this "mess up after an upgrade" of which you speak?

I've used multiple versions of LVM on multiple machines across multiple 
distros for multiple years and never once heard of anyone having a problem 
with it let along experienced one myself.

Shades of FUD methinks.



-- 
alan dot mckinnon at gmail dot com

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Volker Armin Hemmann]

On Thursday 24 March 2011 15:38:02 J. Roeleveld wrote:
> On Thu, March 24, 2011 12:30 pm, Volker Armin Hemmann wrote:
> > On Thursday 24 March 2011 08:49:52 J. Roeleveld wrote:
> >> On Wed, March 23, 2011 5:43 pm, Volker Armin Hemmann wrote:
> >> > md raid devices can do barriers. Don't know about lvm. But lvm is
> >> > such
> >> 
> >> a
> >> 
> >> > can
> >> > of worms I am surprised people still recommend it.
> >> 
> >> What is wrong with LVM?
> >> I've been using it successfully without any issues for years now.
> >> It does what it says on the box.
> > 
> > it is another layer that can go wrong. Why take the risk? There
> > are enough cases of breakage after upgrades - and besides snapshots...
> > is
> > the
> > amount of additional code running really worth it? Especially with bind
> > mounting?
> 
> There are always things that can go wrong and I agree, adding additional
> layers can increase the risk.
> However, the benefits of easily and quickly changing the size of
> partitions and creating snapshots for the use of backups are a big enough
> benefit to off-set the risk.
> 
> Bind-mounting is ok, if you use a single filesystem for everything. I have
> partitions that are filled with thousands of small files and partitions
> filled with files are are, on average, at 1GB in size.
> I haven't found a filesystem yet that successfully handles both of these
> with identical performance.
> When I first tested performance I found that a simple "ls" in a partition
> would appear to just hang. This caused performance issues with my
> IMAP-server.
> I switched to a filesystem that better handles large amounts of small
> files and performance increased significantly.
> 
> The way I do backups is that I stop the services, create snapshots and
> then restart the services.

and I don't stop much - I just cp everything on the backup disk ;)

/home is way to full? no problem, just dump all that file crap on some other 
partition and bind mount the directories. No change from user POV (that is 
me). And since /home is on / and that a 64gb ssd resizing is not a topic. That 
1tb raid5 I dump all data on? Again - why resize? I have all in one place and 
bind what I need elsewhere.

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Neil Bothwick]

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On Thu, 24 Mar 2011 12:19:39 -0500, Dale wrote:

> I have never used LVM but when it messes up after a upgrade, as has 
> happened to many others, see if you say the same thing.  I hope your 
> backups are good and they can restore.

I must be one of the luckiest people around. LVM messes up for many
people, yet I've run it on several machines for several years with no
such troubles.. Ditto for ReiserFS, same for XFS too.

Why does this luck not extend to lottery tickets? Maybe because that's
the one area where it is more than apocryphal that most people are
unlucky.


-- 
Neil Bothwick

An unemployed Court Jester is nobody's fool.

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Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Volker Armin Hemmann]

On Thursday 24 March 2011 12:08:02 Alan McKinnon wrote:
> On Thursday 24 March 2011 12:19:39 Dale wrote:
> > I have never used LVM but when it messes up after a upgrade, as has
> > happened to many others, see if you say the same thing.  I hope your
> > backups are good and they can restore.
> 
> What is this "mess up after an upgrade" of which you speak?
> 
> I've used multiple versions of LVM on multiple machines across multiple
> distros for multiple years and never once heard of anyone having a problem
> with it let along experienced one myself.
> 
> Shades of FUD methinks.

http://bugs.gentoo.org/buglist.cgi?quicksearch=lvm
or if you like a bit of history:

http://bugs.gentoo.org/buglist.cgi?quicksearch=ALL+lvm
there you go.

I like this one:
http://bugs.gentoo.org/show_bug.cgi?id=350455

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Dale]

Bill Longman wrote:
> On 03/24/2011 11:17 AM, Dale wrote:
>    
>> kashani wrote:
>>      
>>> On 3/24/2011 10:19 AM, Dale wrote:
>>>        
>>>> I have never used LVM but when it messes up after a upgrade, as has
>>>> happened to many others, see if you say the same thing. I hope your
>>>> backups are good and they can restore.
>>>>
>>>> Dale
>>>>          
>>>      Meh, boot a liveCD and fix it which took all of 15 minutes. I
>>> don't see that as a failing of LVM, but of Gentoo for lack of another
>>> culprit. You can only roll your OS forward in so many ways before you
>>> have to do a little offline plumbing. May as well complain that you
>>> had to shutdown your machine to put in more RAM.
>>>
>>> kashani
>>>
>>>
>>>        
>> I researched using LVM a good while back.  The reason I didn't was what
>> I posted.  It is prone to problems that are difficult if not impossible
>> to correct.  I may not have data that is worth much but I don't want to
>> loose it either way.
>>
>> People that have read these posts can't plead ignorance.
>>      
> Yet you, who "have never used LVM" *can* plead knowledge?
> Uh....something's really wrong in this formula.
>
>    

Yep, I read about others having problems and loosing data.

Dale

:-)  :-)

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Joost Roeleveld]

On Thursday 24 March 2011 12:19:39 Dale wrote:
> J. Roeleveld wrote:
> > On Thu, March 24, 2011 12:30 pm, Volker Armin Hemmann wrote:
> >> On Thursday 24 March 2011 08:49:52 J. Roeleveld wrote:
> >>> On Wed, March 23, 2011 5:43 pm, Volker Armin Hemmann wrote:
> >>>> md raid devices can do barriers. Don't know about lvm. But lvm is
> >>>> such
> >>> 
> >>> a
> >>> 
> >>>> can
> >>>> of worms I am surprised people still recommend it.
> >>> 
> >>> What is wrong with LVM?
> >>> I've been using it successfully without any issues for years now.
> >>> It does what it says on the box.
> >> 
> >> it is another layer that can go wrong. Why take the risk? There
> >> are enough cases of breakage after upgrades - and besides snapshots...
> >> is the
> >> amount of additional code running really worth it? Especially with
> >> bind
> >> mounting?
> > 
> > There are always things that can go wrong and I agree, adding additional
> > layers can increase the risk.
> > However, the benefits of easily and quickly changing the size of
> > partitions and creating snapshots for the use of backups are a big
> > enough
> > benefit to off-set the risk.
> > 
> > Bind-mounting is ok, if you use a single filesystem for everything. I
> > have partitions that are filled with thousands of small files and
> > partitions filled with files are are, on average, at 1GB in size.
> > I haven't found a filesystem yet that successfully handles both of these
> > with identical performance.
> > When I first tested performance I found that a simple "ls" in a
> > partition
> > would appear to just hang. This caused performance issues with my
> > IMAP-server.
> > I switched to a filesystem that better handles large amounts of small
> > files and performance increased significantly.
> > 
> > The way I do backups is that I stop the services, create snapshots and
> > then restart the services.
> > I then have plenty of time to backup the snapshot.
> > If I were to do this differently, I'd end up having a downtime for over
> > an hour just for a backup.
> > Now, it's barely a minute of downtime.
> > 
> > That, to me, is a very big bonus.
> > 
> > --
> > Joost
> 
> I have never used LVM but when it messes up after a upgrade, as has
> happened to many others, see if you say the same thing.  I hope your
> backups are good and they can restore.
> 
> Dale
> 
> :-)  :-)

Backups are good and I can restore.
Usually need them when I mess things up and accidentally delete files I wanted 
to keep....

LVM may mess up if something goes wrong, but as the LVM-tools backup the 
metadata for LVM, it is trivial to restore and I have not lost any data 
because of issues like that. :)

--
Joost

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Joost Roeleveld]

On Thursday 24 March 2011 22:07:28 Volker Armin Hemmann wrote:
> On Thursday 24 March 2011 12:08:02 Alan McKinnon wrote:
> > On Thursday 24 March 2011 12:19:39 Dale wrote:
> > > I have never used LVM but when it messes up after a upgrade, as has
> > > happened to many others, see if you say the same thing.  I hope your
> > > backups are good and they can restore.
> > 
> > What is this "mess up after an upgrade" of which you speak?
> > 
> > I've used multiple versions of LVM on multiple machines across multiple
> > distros for multiple years and never once heard of anyone having a
> > problem with it let along experienced one myself.
> > 
> > Shades of FUD methinks.
> 
> http://bugs.gentoo.org/buglist.cgi?quicksearch=lvm
> or if you like a bit of history:

Not all of these are LVM, some are only shown because they're related to llvm 
(Which is a virtual machine), but lets ignore those all-together :)

On the first page, at first glance, I don't see any serious ones that are only 
LVM.
The boot-issue was caused by genkernel not being up-to-date with name-changes.

> http://bugs.gentoo.org/buglist.cgi?quicksearch=ALL+lvm
> there you go.

See above

> I like this one:
> http://bugs.gentoo.org/show_bug.cgi?id=350455

Looks like an issue with heavy I/O, affecting the LVM layer trying to lock the 
filesystem.

But I wonder if he's not running into a known issue (which can easily be 
worked around) where pvmove has a memory-leak with the reporting. (eg. the bit 
that checks the progress every 5 seconds, reducing that to every 5 minutes 
significantly reduces that)
However, I do believe this (mem-leak) was fixed.

Am curious what the result will be of that. Please note, I do not run masked 
(~amd64) kernels.

Kind regards,

Joost Roeleveld

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Volker Armin Hemmann]

On Friday 25 March 2011 07:51:13 Joost Roeleveld wrote:
> On Thursday 24 March 2011 22:07:28 Volker Armin Hemmann wrote:
> > On Thursday 24 March 2011 12:08:02 Alan McKinnon wrote:
> > > On Thursday 24 March 2011 12:19:39 Dale wrote:
> > > > I have never used LVM but when it messes up after a upgrade, as
> > > > has
> > > > happened to many others, see if you say the same thing.  I hope
> > > > your
> > > > backups are good and they can restore.
> > > 
> > > What is this "mess up after an upgrade" of which you speak?
> > > 
> > > I've used multiple versions of LVM on multiple machines across
> > > multiple
> > > distros for multiple years and never once heard of anyone having a
> > > problem with it let along experienced one myself.
> > > 
> > > Shades of FUD methinks.
> > 
> > http://bugs.gentoo.org/buglist.cgi?quicksearch=lvm
> 
> > or if you like a bit of history:
> Not all of these are LVM, some are only shown because they're related to
> llvm (Which is a virtual machine), but lets ignore those all-together :)

I know, I am just too lazy to do a more 'sophisticated' search.

> 
> On the first page, at first glance, I don't see any serious ones that are
> only LVM.
> The boot-issue was caused by genkernel not being up-to-date with
> name-changes.
> 
> > http://bugs.gentoo.org/buglist.cgi?quicksearch=ALL+lvm
> > there you go.
> 
> See above

see above. But if you look only at the lvm bugs there are enough examples of 
bad kernel/lvm/whatever interaction. It does not matter that it was baselayout 
or another update that stopped lvm from working. If your system does not boot 
it does not boot - lvm seems to make that more likely.

> 
> > I like this one:
> > http://bugs.gentoo.org/show_bug.cgi?id=350455
> 
> Looks like an issue with heavy I/O, affecting the LVM layer trying to lock
> the filesystem.
> 
> But I wonder if he's not running into a known issue (which can easily be
> worked around) where pvmove has a memory-leak with the reporting. (eg. the
> bit that checks the progress every 5 seconds, reducing that to every 5
> minutes significantly reduces that)
> However, I do believe this (mem-leak) was fixed.
> 
> Am curious what the result will be of that. Please note, I do not run masked
> (~amd64) kernels.

oh, even better, a memory leak. pvmove even. I remember one bug where a 
commenter mentioned that pvmove nuked all data on a non-lvm partition. Great 
stuff.
It does not matter that you might not run 'unstable' kernels. Some people like 
to be a bit more update for very valid reasons (drivers). With lvms history 
that doesn't look so good. 

Re: [gentoo-user] the best filesystem for server: XFS or JFS (or?)

[Elaine C. Sharpe]

In linux.gentoo.user, you wrote:
>
> the best filesystem for you is the one you have
> tested and found best suits your needs.
>

I agree with that part of what you said (which is why I've stuck with 
ext3 for so long), but the rest may have been a tad harsh.

-- 
...she kept arranging and rearranging the rabbit and kind of waving to it. I decided, "this is the person I want to sit next to".

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Elaine C. Sharpe]

In linux.gentoo.user, you wrote:
> Bill Longman wrote:
>> On 03/24/2011 11:17 AM, Dale wrote:
>>    
>>> kashani wrote:
>>>      
>>>> On 3/24/2011 10:19 AM, Dale wrote:
>>>>        
>>>>> I have never used LVM but when it messes up after a upgrade, as has
>>>>> happened to many others, see if you say the same thing. I hope your
>>>>> backups are good and they can restore.
>>>>>
>>>>> Dale
>>>>>          
>>>>      Meh, boot a liveCD and fix it which took all of 15 minutes. I
>>>> don't see that as a failing of LVM, but of Gentoo for lack of another
>>>> culprit. You can only roll your OS forward in so many ways before you
>>>> have to do a little offline plumbing. May as well complain that you
>>>> had to shutdown your machine to put in more RAM.
>>>>
>>>> kashani
>>>>
>>>>
>>>>        
>>> I researched using LVM a good while back.  The reason I didn't was what
>>> I posted.  It is prone to problems that are difficult if not impossible
>>> to correct.  I may not have data that is worth much but I don't want to
>>> loose it either way.
>>>
>>> People that have read these posts can't plead ignorance.
>>>      
>> Yet you, who "have never used LVM" *can* plead knowledge?
>> Uh....something's really wrong in this formula.
>>
>>    
>
> Yep, I read about others having problems and loosing data.
>
> Dale
>
>:-)  :-)

You can read about others having problems and losing data with pretty 
much every bit of software ever coded. *Lots* of people are not particularly 
competent and write horroe stories or bad reviews without bothering to
mention the errors they made which actually caused the problem.
I see evidence of that on this very list daily. So IMO your method is 
a bit suspect. :)

-- 
...she kept arranging and rearranging the rabbit and kind of waving to it. I decided, "this is the person I want to sit next to".

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Dale]

Elaine C. Sharpe wrote:
> In linux.gentoo.user, you wrote:
>    
>>
>> Yep, I read about others having problems and loosing data.
>>
>> Dale
>>
>> :-)  :-)
>>      
> You can read about others having problems and losing data with pretty
> much every bit of software ever coded. *Lots* of people are not particularly
> competent and write horroe stories or bad reviews without bothering to
> mention the errors they made which actually caused the problem.
> I see evidence of that on this very list daily. So IMO your method is
> a bit suspect. :)
>
>    

The opposite can be said too.  I seem to recall hal working for a lot of 
people but for me, it was a miserable failure and forced me into a hard 
reset.

Just because something works for most people, doesn't mean it will for 
everyone either.  If you lose data, it doesn't matter.  LVM just adds 
one more layer of something to go wrong.  Me, I don't need the extra 
risk of having a system that doesn't boot and a loss of data.  I'm sure 
there are a lot of people that see it the way I do too.  They just don't 
need the extra risk.

Dale

:-)  :-)

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Elaine C. Sharpe]

In linux.gentoo.user, you wrote:
> Elaine C. Sharpe wrote:
>> In linux.gentoo.user, you wrote:
>>    
>>>
>>> Yep, I read about others having problems and loosing data.
>>>
>>> Dale
>>>
>>> :-)  :-)
>>>      
>> You can read about others having problems and losing data with pretty
>> much every bit of software ever coded. *Lots* of people are not particularly
>> competent and write horroe stories or bad reviews without bothering to
>> mention the errors they made which actually caused the problem.
>> I see evidence of that on this very list daily. So IMO your method is
>> a bit suspect. :)
>>
>>    
>
> The opposite can be said too.  I seem to recall hal working for a lot of 
> people but for me, it was a miserable failure and forced me into a hard 
> reset.
>

So, if your method doesn't really work very well but you invert it and 
see that then it doesn't work well either that validates the original choice?
:)

> Just because something works for most people, doesn't mean it will for 
> everyone either.  If you lose data, it doesn't matter.  LVM just adds 
> one more layer of something to go wrong.  Me, I don't need the extra 
> risk of having a system that doesn't boot and a loss of data.  I'm sure 
> there are a lot of people that see it the way I do too.  They just don't 
> need the extra risk.
>

Using the least number of layers of abstraction you can get away with is
a perfectly valid criteria. What I was pointing out was that informal
polls of users with a sad story to tell is not a very effective way to 
conduct research. People say all kinds of things that just aren't true.

-- 
...she kept arranging and rearranging the rabbit and kind of waving to it. I decided, "this is the person I want to sit next to".

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Alan McKinnon]

On Saturday 26 March 2011 15:06:31 Elaine C. Sharpe wrote:
> > Just because something works for most people, doesn't mean it will for 
> > everyone either.  If you lose data, it doesn't matter.  LVM just adds 
> > one more layer of something to go wrong.  Me, I don't need the extra 
> > risk of having a system that doesn't boot and a loss of data.  I'm sure 
> > there are a lot of people that see it the way I do too.  They just
> > don't 
> > need the extra risk.
> 
> Using the least number of layers of abstraction you can get away with is
> a perfectly valid criteria. What I was pointing out was that informal
> polls of users with a sad story to tell is not a very effective way to 
> conduct research. People say all kinds of things that just aren't true.

There's an elephant in this room. The number of actual layers is greater than 
just LVM plus FS. It's whatever the BIOS (or a reasonable substitute is 
doing), plus the drive firmware, kernel driver(s) - there's more than one of 
those - plus any RAID in use (hardware or software) and finally the file 
system.

That's a lot of layers, a lot of code, a lot of opportunity for people to 
reveal the extent of their lack of knowledge. I've often heard it said that 
code like ZFS and brtfs eliminates several of these layers therefore it's 
technically a better option. That may be true, but let me just point out that 
whatever LVM+fs+other_stuff is doing as separate chunks of code also gets done 
by ZFS etc. You just don't see it, and just because it's abstracted away 
doesn't mean it's not there.

-- 
alan dot mckinnon at gmail dot com

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Neil Bothwick]

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On Sat, 26 Mar 2011 13:17:41 -0500, Dale wrote:

> Just because something works for most people, doesn't mean it will for 
> everyone either.  If you lose data, it doesn't matter.  LVM just adds 
> one more layer of something to go wrong.  Me, I don't need the extra 
> risk of having a system that doesn't boot and a loss of data.  I'm sure 
> there are a lot of people that see it the way I do too.  They just
> don't need the extra risk.

On the other hand, the OP needed a feature that LVM provides very well.
If you don't need anything a product, be it software or a new fridge,
provides, why bother with it? But that's not the case here.

See "random" sig for further comment :-O


-- 
Neil Bothwick

"Good Enough" is the death knell of progress.

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Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Dale]

Alan McKinnon wrote:
> On Saturday 26 March 2011 15:06:31 Elaine C. Sharpe wrote:
>    
>>> Just because something works for most people, doesn't mean it will for
>>> everyone either.  If you lose data, it doesn't matter.  LVM just adds
>>> one more layer of something to go wrong.  Me, I don't need the extra
>>> risk of having a system that doesn't boot and a loss of data.  I'm sure
>>> there are a lot of people that see it the way I do too.  They just
>>> don't
>>> need the extra risk.
>>>        
>> Using the least number of layers of abstraction you can get away with is
>> a perfectly valid criteria. What I was pointing out was that informal
>> polls of users with a sad story to tell is not a very effective way to
>> conduct research. People say all kinds of things that just aren't true.
>>      
> There's an elephant in this room. The number of actual layers is greater than
> just LVM plus FS. It's whatever the BIOS (or a reasonable substitute is
> doing), plus the drive firmware, kernel driver(s) - there's more than one of
> those - plus any RAID in use (hardware or software) and finally the file
> system.
>
> That's a lot of layers, a lot of code, a lot of opportunity for people to
> reveal the extent of their lack of knowledge. I've often heard it said that
> code like ZFS and brtfs eliminates several of these layers therefore it's
> technically a better option. That may be true, but let me just point out that
> whatever LVM+fs+other_stuff is doing as separate chunks of code also gets done
> by ZFS etc. You just don't see it, and just because it's abstracted away
> doesn't mean it's not there.
>
>    

I'll add this.  Alan if I recall correctly runs a lot of systems.  He 
has a boatload of experience using all sorts of software/hardware.  Me, 
I don't.  For the longest, I had one system and that was it.  If I 
upgrade my kernel, LVM, or some package that LVM depends on and I can't 
boot, I'm screwed.  If I can't boot, I can't google anything to find out 
how to fix it.  I also don't know enough about LVM to fix it myself.  
Since there is so many layers of things that can already go wrong on a 
system, adding one more layer that can be complicated only makes a 
problem grow.

I'm sure Alan and many others could go out and buy or build a new system 
and put LVM on it and fix about any problem that comes along.  Thing is, 
there are others that can't.  Add to this that when I was thinking about 
using it, I read where a lot of people, for whatever reason, couldn't 
get it back working again and lost data.  For me, I don't care if it was 
LVM itself, the kernel or some combination of other things, if I can't 
boot or lose data, the result is the same.  I can fix a kernel problem, 
a broken package but if LVM fails, I'm stuck.

That said, I now have a second rig.  I may at some point use LVM because 
I can always go to the other room and use my old rig to get help.  I 
already have a 750Gb drive that is about full of pictures, I got a 
camera and get a little happy at times, and videos I have downloaded, 
everything from TV series to stuff off youtube.  I may buy another large 
drive and use LVM or something to give me more room since I really don't 
want to have to break up my filing system across two separate drives.  I 
won't consider putting the booting part of my OS on LVM tho.

Of course, I did see a 3Tb drive on sale the other day at newegg.  o_O  
That would last a while.  ;-)

Dale

:-)  :-)

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Mark Knecht]

On Sat, Mar 26, 2011 at 3:20 PM, Dale <rdalek1967@gmail.com> wrote:
> Alan McKinnon wrote:
>>
>> On Saturday 26 March 2011 15:06:31 Elaine C. Sharpe wrote:
>>
>>>>
>>>> Just because something works for most people, doesn't mean it will for
>>>> everyone either.  If you lose data, it doesn't matter.  LVM just adds
>>>> one more layer of something to go wrong.  Me, I don't need the extra
>>>> risk of having a system that doesn't boot and a loss of data.  I'm sure
>>>> there are a lot of people that see it the way I do too.  They just
>>>> don't
>>>> need the extra risk.
>>>>
>>>
>>> Using the least number of layers of abstraction you can get away with is
>>> a perfectly valid criteria. What I was pointing out was that informal
>>> polls of users with a sad story to tell is not a very effective way to
>>> conduct research. People say all kinds of things that just aren't true.
>>>
>>
>> There's an elephant in this room. The number of actual layers is greater
>> than
>> just LVM plus FS. It's whatever the BIOS (or a reasonable substitute is
>> doing), plus the drive firmware, kernel driver(s) - there's more than one
>> of
>> those - plus any RAID in use (hardware or software) and finally the file
>> system.
>>
>> That's a lot of layers, a lot of code, a lot of opportunity for people to
>> reveal the extent of their lack of knowledge. I've often heard it said
>> that
>> code like ZFS and brtfs eliminates several of these layers therefore it's
>> technically a better option. That may be true, but let me just point out
>> that
>> whatever LVM+fs+other_stuff is doing as separate chunks of code also gets
>> done
>> by ZFS etc. You just don't see it, and just because it's abstracted away
>> doesn't mean it's not there.
>>
>>
>
> I'll add this.  Alan if I recall correctly runs a lot of systems.  He has a
> boatload of experience using all sorts of software/hardware.  Me, I don't.
>  For the longest, I had one system and that was it.  If I upgrade my kernel,
> LVM, or some package that LVM depends on and I can't boot, I'm screwed.  If
> I can't boot, I can't google anything to find out how to fix it.  I also
> don't know enough about LVM to fix it myself.  Since there is so many layers
> of things that can already go wrong on a system, adding one more layer that
> can be complicated only makes a problem grow.
>
> I'm sure Alan and many others could go out and buy or build a new system and
> put LVM on it and fix about any problem that comes along.  Thing is, there
> are others that can't.  Add to this that when I was thinking about using it,
> I read where a lot of people, for whatever reason, couldn't get it back
> working again and lost data.  For me, I don't care if it was LVM itself, the
> kernel or some combination of other things, if I can't boot or lose data,
> the result is the same.  I can fix a kernel problem, a broken package but if
> LVM fails, I'm stuck.
>
> That said, I now have a second rig.  I may at some point use LVM because I
> can always go to the other room and use my old rig to get help.  I already
> have a 750Gb drive that is about full of pictures, I got a camera and get a
> little happy at times, and videos I have downloaded, everything from TV
> series to stuff off youtube.  I may buy another large drive and use LVM or
> something to give me more room since I really don't want to have to break up
> my filing system across two separate drives.  I won't consider putting the
> booting part of my OS on LVM tho.
>
> Of course, I did see a 3Tb drive on sale the other day at newegg.  o_O  That
> would last a while.  ;-)
>
> Dale
>
> :-)  :-)

Dale,
   I understand your position and concerns. While I have a number of
systems, I have little time or patience for dealing with a lot of this
stuff and LVM has been one of them.

   One thing I'm considering to try out LVM is a second Gentoo
installation on an already running system. It will either be a 50GB
partition of its own, or a Virtualbox VM. I'd do the normal Gentoo
install for LVM, figure out how it works, etc., and then decide if I
want to use it in the future.

   After all, as Neil said, if something offers features we don't feel
we need then why buy it?

- Mark

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Alan McKinnon]

On Saturday 26 March 2011 17:20:48 Dale wrote:
> Alan McKinnon wrote:
> > On Saturday 26 March 2011 15:06:31 Elaine C. Sharpe wrote:
> >>> Just because something works for most people, doesn't mean it will
> >>> for
> >>> everyone either.  If you lose data, it doesn't matter.  LVM just
> >>> adds
> >>> one more layer of something to go wrong.  Me, I don't need the extra
> >>> risk of having a system that doesn't boot and a loss of data.  I'm
> >>> sure
> >>> there are a lot of people that see it the way I do too.  They just
> >>> don't
> >>> need the extra risk.
> >> 
> >> Using the least number of layers of abstraction you can get away with
> >> is
> >> a perfectly valid criteria. What I was pointing out was that informal
> >> polls of users with a sad story to tell is not a very effective way to
> >> conduct research. People say all kinds of things that just aren't
> >> true.
> > 
> > There's an elephant in this room. The number of actual layers is greater
> > than just LVM plus FS. It's whatever the BIOS (or a reasonable
> > substitute is doing), plus the drive firmware, kernel driver(s) -
> > there's more than one of those - plus any RAID in use (hardware or
> > software) and finally the file system.
> > 
> > That's a lot of layers, a lot of code, a lot of opportunity for people
> > to
> > reveal the extent of their lack of knowledge. I've often heard it said
> > that code like ZFS and brtfs eliminates several of these layers
> > therefore it's technically a better option. That may be true, but let
> > me just point out that whatever LVM+fs+other_stuff is doing as separate
> > chunks of code also gets done by ZFS etc. You just don't see it, and
> > just because it's abstracted away doesn't mean it's not there.
> 
> I'll add this.  Alan if I recall correctly runs a lot of systems.  He
> has a boatload of experience using all sorts of software/hardware.  Me,
> I don't.  For the longest, I had one system and that was it.  If I
> upgrade my kernel, LVM, or some package that LVM depends on and I can't
> boot, I'm screwed.  If I can't boot, I can't google anything to find out
> how to fix it.  I also don't know enough about LVM to fix it myself.
> Since there is so many layers of things that can already go wrong on a
> system, adding one more layer that can be complicated only makes a
> problem grow.

Yeah, I have a boatload of stuff. Also a boatload of project managers and 
sales people but that's another story.

All I'm saying is that being put off a particular package due to having read 
something somewhere that it might be broken for somebody sometime makes no 
sense. There are heaps of other packages you use right now that fall in 
exactly the same category - critical stuff that can make a system unbootable. 
But you use them. Heck, you even used XFS if memory serves, and that was brave 
indeed. Far, far braver than using LVM with a much higher risk - and that's 
from features, not bugs.

If fear of not being able to recover from a problem that is not likely to hit 
you is the driving factor, then you might as well sell the pcs and go onto to 
doing something else. But if I were you I wouldn't sell myself so short, we've 
both been around here for many a year now and you've yet to suffer a 
catastrophic unrecoverable failure, right? I read your posts, I know many 
pretenders to the title of "sysadmin" that would just reinstall when faced 
with some of the now routine stuff you've dealt with. Like emerge won't work 
after a python update - wanna bet money on the percentage of people that would 
floor?

:-)






> 
> I'm sure Alan and many others could go out and buy or build a new system
> and put LVM on it and fix about any problem that comes along.  Thing is,
> there are others that can't.  Add to this that when I was thinking about
> using it, I read where a lot of people, for whatever reason, couldn't
> get it back working again and lost data.  For me, I don't care if it was
> LVM itself, the kernel or some combination of other things, if I can't
> boot or lose data, the result is the same.  I can fix a kernel problem,
> a broken package but if LVM fails, I'm stuck.
> 
> That said, I now have a second rig.  I may at some point use LVM because
> I can always go to the other room and use my old rig to get help.  I
> already have a 750Gb drive that is about full of pictures, I got a
> camera and get a little happy at times, and videos I have downloaded,
> everything from TV series to stuff off youtube.  I may buy another large
> drive and use LVM or something to give me more room since I really don't
> want to have to break up my filing system across two separate drives.  I
> won't consider putting the booting part of my OS on LVM tho.
> 
> Of course, I did see a 3Tb drive on sale the other day at newegg.  o_O
> That would last a while.  ;-)
> 
> Dale
> 
> :-)  :-)
-- 
alan dot mckinnon at gmail dot com

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Alan McKinnon]

On Saturday 26 March 2011 15:36:19 Mark Knecht wrote:
> Dale,
>    I understand your position and concerns. While I have a number of
> systems, I have little time or patience for dealing with a lot of this
> stuff and LVM has been one of them.
> 
>    One thing I'm considering to try out LVM is a second Gentoo
> installation on an already running system. It will either be a 50GB
> partition of its own, or a Virtualbox VM. I'd do the normal Gentoo
> install for LVM, figure out how it works, etc., and then decide if I
> want to use it in the future.

Well I can help with that, or at least provide some tips. Delivering Red Hat's 
training courses exposes you to all the weird and wonderful ways people 
misunderstand LVM and the even weirder ways gnome tools present the subject...

Logically, LVM sits between your physical disks (or raid arrays if you use 
that) and the filesystem. All it is is a way to manipulate these things called 
"block devices" in ways that you normally can't do without LVM.

Like if you have 4 partitions on a disk and want to make the third one bigger. 
Using just fdisk, you can't do that without making backups and restoring. Or 
creating a filesystem larger than any one disk.

So LVM takes a bunch of disks or arrays and lets you combine them in ways you 
want them (not ways the hardware forces you to have them). And that's all it 
does - forget all the nonsense in the man pages about aligning stripes to make 
mirrors - that just confuses people and makes them think it's some fancy raid.

You could argue that LVM exposes too much complexity  by letting you see the 
physical volumes (pv), volume groups (vg) and logical volumes (lv), and I 
won't argue with that. It's a trade between flexibility and complexity. I'm 
happy with it, others might not be.



-- 
alan dot mckinnon at gmail dot com

Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

[Peter Humphrey]

On Saturday 26 March 2011 23:46:26 Alan McKinnon wrote:

> So LVM takes a bunch of disks or arrays and lets you combine them in ways
> you want them (not ways the hardware forces you to have them). And
> that's all it does

I also find it handy for creating more partitions than the standard hardware 
schemes allow - it used to be 12 on a SCSI disk and 15 on IDE; I haven't 
bothered to find out what SATA allows.

This wouldn't usually matter on a production system, but experimenting with 
other distros is eased by using LVM. So is creating several swap partitions 
with different sizes and priorities: small ones for normal use and big ones 
for compiling Open Office - that sort of thing.

-- 
Rgds
Peter