[gentoo-user] {OT} SSD instead of RAID1?

[gentoo-user] {OT} SSD instead of RAID1?

[Grant]

I have two local systems that need to be reliable and also have a
large storage capacity.  The thing is, the data storage doesn't need
to be reliable, I just need the systems to keep running.  The data on
the systems is backed up and losing it wouldn't be the end of the
world because of the backups.  However, I really need each of the
systems to keep running.

I've read that an SSD drive should be much more reliable than an HD
drive.  What if I bought a low-price/low-capacity SSD drive for each
of these systems, installed the system essentials on them, and used my
existing high-capacity HD drives for data storage?  Would each system
keep running if the HDs died?  If so, I think that would offer as good
or better system reliability than RAID1.  What do you think?

- Grant

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Stroller]

On 26 Jul 2009, at 11:46, Grant wrote:
> ... What if I bought a low-price/low-capacity SSD drive for each
> of these systems, installed the system essentials on them, and used my
> existing high-capacity HD drives for data storage?  Would each system
> keep running if the HDs died?  If so, I think that would offer as good
> or better system reliability than RAID1.  What do you think?

You don't need to buy SSD "drives" - instead you could use CF cards  
and a cheap adaptor. These are commensurate in capacity & cost with  
USB flash drives (4gig, maybe 16gig?), but CF cards "talk EIDE" and  
you can get cheap pin-convertors allowing you to connect them to EIDE  
cables and treat them like a hard-drive.

I know of these used in Asterisk based PABX systems & PoS tills with  
the expectation that they're more reliable than disks, and have read  
statements by people deploying quantities of such machines that  
they've never had a failure in years of use.

I don't know how that really compares to RAID 1 - if you use hardware  
RAID (and you can get hardware SATA controllers for £50 these days)  
then you can assign a hot-spare, and hot-swap a replacement drive with  
zero downtime. With hardware RAID you can still boot if one of the  
drives fails, but you do add the controller as a potential point-of- 
failure.

Stroller.

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Grant]

>> ... What if I bought a low-price/low-capacity SSD drive for each
>> of these systems, installed the system essentials on them, and used my
>> existing high-capacity HD drives for data storage?  Would each system
>> keep running if the HDs died?  If so, I think that would offer as good
>> or better system reliability than RAID1.  What do you think?
>
> You don't need to buy SSD "drives" - instead you could use CF cards and a
> cheap adaptor. These are commensurate in capacity & cost with USB flash
> drives (4gig, maybe 16gig?), but CF cards "talk EIDE" and you can get cheap
> pin-convertors allowing you to connect them to EIDE cables and treat them
> like a hard-drive.

Aren't CF cards much slower than SSD drives and HD drives?

> I know of these used in Asterisk based PABX systems & PoS tills with the
> expectation that they're more reliable than disks, and have read statements
> by people deploying quantities of such machines that they've never had a
> failure in years of use.

I like the sound of that.

> I don't know how that really compares to RAID 1 - if you use hardware RAID
> (and you can get hardware SATA controllers for £50 these days) then you can
> assign a hot-spare, and hot-swap a replacement drive with zero downtime.
> With hardware RAID you can still boot if one of the drives fails, but you do
> add the controller as a potential point-of-failure.

Would the system keeping running if I used a CF or SSD for the system
install and the HD drive died?

- Grant

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Florian Philipp]

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Grant schrieb:
>>> ... What if I bought a low-price/low-capacity SSD drive for each
>>> of these systems, installed the system essentials on them, and used my
>>> existing high-capacity HD drives for data storage?  Would each system
>>> keep running if the HDs died?  If so, I think that would offer as good
>>> or better system reliability than RAID1.  What do you think?
>> You don't need to buy SSD "drives" - instead you could use CF cards and a
>> cheap adaptor. These are commensurate in capacity & cost with USB flash
>> drives (4gig, maybe 16gig?), but CF cards "talk EIDE" and you can get cheap
>> pin-convertors allowing you to connect them to EIDE cables and treat them
>> like a hard-drive.
> 
> Aren't CF cards much slower than SSD drives and HD drives?
> 

Yep, especially the cheap ones which do not support DMA, just PIO. But
this is not necessarily a problem: After starting all services etc.
there will be very few reads on stuff like /etc and /usr. Just make sure
to put all directories to which you write (parts of /var like /var/log
and the several tmp directories) on an HDD, NFS or tmpfs. Of course,
this all depends on your usage patterns and how much RAM you have.

If you really need to write to the CFDisk, make sure to buy one with DMA
support (and no, the label "super fast" which is regularly found on
these things does not necessarily mean that it supports DMA).

One drawback of this configuration: You can never use swap - never!
Neither on the HDD (there is a high chance that the system would crash
when the HDD fails) nor on the (cheap) SSD/flash drive (the drive would
wear down, removing any advantage you tried to gain).

>> I know of these used in Asterisk based PABX systems & PoS tills with the
>> expectation that they're more reliable than disks, and have read statements
>> by people deploying quantities of such machines that they've never had a
>> failure in years of use.
> 
> I like the sound of that.

Where I work, we have a System-on-a-Chip (SoC) NAS. Albeit being the
second most powerful machine we have in our server room (quad core CPU,
lots of RAM, three redundant power supplies and a good dozen HDDs), the
OSS itself resides on a removable card not bigger than my thumb.

> 
>> I don't know how that really compares to RAID 1 - if you use hardware RAID
>> (and you can get hardware SATA controllers for £50 these days) then you can
>> assign a hot-spare, and hot-swap a replacement drive with zero downtime.
>> With hardware RAID you can still boot if one of the drives fails, but you do
>> add the controller as a potential point-of-failure.
> 
> Would the system keeping running if I used a CF or SSD for the system
> install and the HD drive died?
> 
> - Grant
> 



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Re: [gentoo-user] {OT} SSD instead of RAID1?

[Florian Philipp]

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Florian Philipp schrieb:
> 
> Where I work, we have a System-on-a-Chip (SoC) NAS. Albeit being the
> second most powerful machine we have in our server room (quad core CPU,
> lots of RAM, three redundant power supplies and a good dozen HDDs), the
> OSS itself resides on a removable card not bigger than my thumb.
> 


Err, I don't know if I really have to make this clarification, but I
don't want to spread false nomenclature:

Of course, the system I describe is not really an SoC because not all
components reside on a single chip. Actually, only the basic
input/output system and persistent storage are built as an SoC or, to be
more precise, as a System-in-a-Package (SiP).


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Re: [gentoo-user] {OT} SSD instead of RAID1?

[James Ausmus]

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On Mon, Jul 27, 2009 at 10:43 AM, Florian Philipp <
lists@f_philipp.fastmail.net> wrote:

> Grant schrieb:
>

<snip>


> >> You don't need to buy SSD "drives" - instead you could use CF cards and
> a
> >> cheap adaptor. These are commensurate in capacity & cost with USB flash
> >> drives (4gig, maybe 16gig?), but CF cards "talk EIDE" and you can get
> cheap
> >> pin-convertors allowing you to connect them to EIDE cables and treat
> them
> >> like a hard-drive.
> >
> > Aren't CF cards much slower than SSD drives and HD drives?
> >
>

<snip>


>
> If you really need to write to the CFDisk, make sure to buy one with DMA
> support (and no, the label "super fast" which is regularly found on
> these things does not necessarily mean that it supports DMA).


One thing to watch out for if you do go the CF/DMA route - be careful what
CF<->IDE/SATA adapter you buy - in an embedded control system project I
worked on a few years ago, we went CF + adapter for the primary OS driver,
got a super-fast 4GB CF card, and couldn't use the speed of it at all,
because the cheapo CF adapter we got was so electrically noisy across the
physical adapter pins, that DMA reads/writes would fail, and the speed would
get auto-reduced to PIO. Very, very, very annoying. If you get a CF adapter,
make sure to spend the extra $5-20 (or however much, I haven't priced in
quite a while) to get something that will be compatible with the transfer
speeds that you are wanting to use.

-James

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Re: [gentoo-user] {OT} SSD instead of RAID1?

[Grant]

>>>> ... What if I bought a low-price/low-capacity SSD drive for each
>>>> of these systems, installed the system essentials on them, and used my
>>>> existing high-capacity HD drives for data storage?  Would each system
>>>> keep running if the HDs died?  If so, I think that would offer as good
>>>> or better system reliability than RAID1.  What do you think?
>>> You don't need to buy SSD "drives" - instead you could use CF cards and a
>>> cheap adaptor. These are commensurate in capacity & cost with USB flash
>>> drives (4gig, maybe 16gig?), but CF cards "talk EIDE" and you can get cheap
>>> pin-convertors allowing you to connect them to EIDE cables and treat them
>>> like a hard-drive.
>>
>> Aren't CF cards much slower than SSD drives and HD drives?
>>
>
> Yep, especially the cheap ones which do not support DMA, just PIO. But
> this is not necessarily a problem: After starting all services etc.
> there will be very few reads on stuff like /etc and /usr. Just make sure
> to put all directories to which you write (parts of /var like /var/log
> and the several tmp directories) on an HDD, NFS or tmpfs. Of course,
> this all depends on your usage patterns and how much RAM you have.
>
> If you really need to write to the CFDisk, make sure to buy one with DMA
> support (and no, the label "super fast" which is regularly found on
> these things does not necessarily mean that it supports DMA).
>
> One drawback of this configuration: You can never use swap - never!
> Neither on the HDD (there is a high chance that the system would crash
> when the HDD fails) nor on the (cheap) SSD/flash drive (the drive would
> wear down, removing any advantage you tried to gain).
>
>>> I know of these used in Asterisk based PABX systems & PoS tills with the
>>> expectation that they're more reliable than disks, and have read statements
>>> by people deploying quantities of such machines that they've never had a
>>> failure in years of use.
>>
>> I like the sound of that.
>
> Where I work, we have a System-on-a-Chip (SoC) NAS. Albeit being the
> second most powerful machine we have in our server room (quad core CPU,
> lots of RAM, three redundant power supplies and a good dozen HDDs), the
> OSS itself resides on a removable card not bigger than my thumb.

Is cost-savings the advantage of using CF instead of SSD?  It sounds
like it might be wiser to spend a little more (low capacity SSD drives
are pretty cheap now) and have a real storage device that doesn't need
an adapter and is much faster, can swap, etc.

I bet I'm missing something though...?

- Grant


>>> I don't know how that really compares to RAID 1 - if you use hardware RAID
>>> (and you can get hardware SATA controllers for £50 these days) then you can
>>> assign a hot-spare, and hot-swap a replacement drive with zero downtime.
>>> With hardware RAID you can still boot if one of the drives fails, but you do
>>> add the controller as a potential point-of-failure.
>>
>> Would the system keeping running if I used a CF or SSD for the system
>> install and the HD drive died?
>>
>> - Grant

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Stroller]

On 28 Jul 2009, at 18:52, Grant wrote:
> ...
> Is cost-savings the advantage of using CF instead of SSD?  It sounds
> like it might be wiser to spend a little more (low capacity SSD drives
> are pretty cheap now) and have a real storage device that doesn't need
> an adapter and is much faster, can swap, etc.

I assumed that you're looking at £100 or more for an SSD, as opposed  
to < £10 for a CF card. I didn't check those prices, however.

Are SSDs really *that* much better than CF cards in terms of write  
cycles? (i.e. swap)
How much swap are you actually using?

If the box is just a NAS, then I can't see the speed of the system  
drive is an issue *at all*.

Stroller.


EDIT: I just checked & a 32gig SATA SSD is £75 including VAT here. The  
headline price is £66, and if it wasn't for the sales tax I'd just  
about consider that much for the convenience. An 8gig CF card is £8,  
and that's perfectly ample space for a headless server. FWIW I went  
for hardware RAID - secondhand 3ware 9500S - & conventional SATA hard- 
drives.

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Grant]

>> Is cost-savings the advantage of using CF instead of SSD?  It sounds
>> like it might be wiser to spend a little more (low capacity SSD drives
>> are pretty cheap now) and have a real storage device that doesn't need
>> an adapter and is much faster, can swap, etc.
>
> I assumed that you're looking at £100 or more for an SSD, as opposed to <
> £10 for a CF card. I didn't check those prices, however.
>
> Are SSDs really *that* much better than CF cards in terms of write cycles?
> (i.e. swap)
> How much swap are you actually using?
>
> If the box is just a NAS, then I can't see the speed of the system drive is
> an issue *at all*.

They're actually workstations so I don't think I should neglect the
performance aspect.  Should this scheme keep the system running if the
HD fails?

/ SSD
/boot SSD
/home HD
swap HD

> Stroller.
>
>
> EDIT: I just checked & a 32gig SATA SSD is £75 including VAT here. The
> headline price is £66, and if it wasn't for the sales tax I'd just about
> consider that much for the convenience. An 8gig CF card is £8, and that's
> perfectly ample space for a headless server. FWIW I went for hardware RAID -
> secondhand 3ware 9500S - & conventional SATA hard-drives.

How much is the CF adapter?  That would narrow the gap, although maybe
not considering a 2.5" -> 3.5" adapter.

Yeah, it looks like ~$80 for a 16GB Super Talent drive.  This one for
~$120 is 32GB and is said to have no stuttering (apparently because of
its internal Indilinx controller):

http://www.newegg.com/Product/Product.aspx?Item=N82E16820609392

Anyway, the point of all this is to prevent an HD failure from
stopping the system.  An SSD is much safer, right?

- Grant

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Florian Philipp]

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Grant schrieb:
>>> Is cost-savings the advantage of using CF instead of SSD?  It sounds
>>> like it might be wiser to spend a little more (low capacity SSD drives
>>> are pretty cheap now) and have a real storage device that doesn't need
>>> an adapter and is much faster, can swap, etc.
>> I assumed that you're looking at £100 or more for an SSD, as opposed to <
>> £10 for a CF card. I didn't check those prices, however.
>>
>> Are SSDs really *that* much better than CF cards in terms of write cycles?
>> (i.e. swap)
>> How much swap are you actually using?
>>
>> If the box is just a NAS, then I can't see the speed of the system drive is
>> an issue *at all*.
> 
> They're actually workstations so I don't think I should neglect the
> performance aspect.  Should this scheme keep the system running if the
> HD fails?
> 
> / SSD
> /boot SSD
> /home HD
> swap HD
> 

No. As I pointed out in one of my earlier posts, you can't put swap on
the HD. It would certainly crash the system when the disk fails.

Better make sure that these systems have that much RAM that they don't
need a swap-partition. Alternatively, buy a decent SSD, not a cheap one,
and swap on that.


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Re: [gentoo-user] {OT} SSD instead of RAID1?

[Grant]

>>>> Is cost-savings the advantage of using CF instead of SSD?  It sounds
>>>> like it might be wiser to spend a little more (low capacity SSD drives
>>>> are pretty cheap now) and have a real storage device that doesn't need
>>>> an adapter and is much faster, can swap, etc.
>>> I assumed that you're looking at £100 or more for an SSD, as opposed to <
>>> £10 for a CF card. I didn't check those prices, however.
>>>
>>> Are SSDs really *that* much better than CF cards in terms of write cycles?
>>> (i.e. swap)
>>> How much swap are you actually using?
>>>
>>> If the box is just a NAS, then I can't see the speed of the system drive is
>>> an issue *at all*.
>>
>> They're actually workstations so I don't think I should neglect the
>> performance aspect.  Should this scheme keep the system running if the
>> HD fails?
>>
>> / SSD
>> /boot SSD
>> /home HD
>> swap HD
>>
>
> No. As I pointed out in one of my earlier posts, you can't put swap on
> the HD. It would certainly crash the system when the disk fails.
>
> Better make sure that these systems have that much RAM that they don't
> need a swap-partition. Alternatively, buy a decent SSD, not a cheap one,
> and swap on that.

OK, that's right.  How can I find out if 4GB RAM (the current amount)
is enough?  From what I understand of how Linux handles memory, it
will fill it up as quickly as possible, and then free it as necessary.
 This makes it difficult to determine how much RAM is necessary from
watching top.

I read on this list that the kernel needs *some* swap, even just a
tiny amount, to function properly.  Is that true?  If so, do you think
it would be OK to put this tiny amount of swap on a cheap SSD?

- Grant

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Neil Bothwick]

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On Thu, 30 Jul 2009 05:17:26 -0700, Grant wrote:

> OK, that's right.  How can I find out if 4GB RAM (the current amount)
> is enough?  From what I understand of how Linux handles memory, it
> will fill it up as quickly as possible, and then free it as necessary.
>  This makes it difficult to determine how much RAM is necessary from
> watching top.

Use free to see how much of the memory is used by buffers and caches.


-- 
Neil Bothwick

I am Tagline of Borg. Prepare to assimilate me.

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Re: [gentoo-user] {OT} SSD instead of RAID1?

[Grant]

>> OK, that's right.  How can I find out if 4GB RAM (the current amount)
>> is enough?  From what I understand of how Linux handles memory, it
>> will fill it up as quickly as possible, and then free it as necessary.
>>  This makes it difficult to determine how much RAM is necessary from
>> watching top.
>
> Use free to see how much of the memory is used by buffers and caches.

Thank you Neil.  On one of my systems, does this tell me that although
I'm using ~952MB, I'm really only using ~474MB and I don't need swap:

# free
             total       used       free     shared    buffers     cached
Mem:       1028780     952240      76540          0     146984     330516
-/+ buffers/cache:     474740     554040
Swap:      2008116      80944    1927172

- Grant

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Alan McKinnon]

On Thursday 30 July 2009 14:17:26 Grant wrote:

> OK, that's right.  How can I find out if 4GB RAM (the current amount)
> is enough?  From what I understand of how Linux handles memory, it
> will fill it up as quickly as possible, and then free it as necessary.
>  This makes it difficult to determine how much RAM is necessary from
> watching top.

top lies. This has been discussed here many times. All your memory tools 
essentially tell you how much memory an app is able to see into, and most of 
that memory is shared with other stuff (like libs).

You can't tell how much memory an app is using in any meaningful way, you are 
not supposed to even look at it as it changes millions of times a second. What 
you are supposed to do is select an allocation algorithm that works well for 
you in practice and let the kernel do the heavy lifting.

Yes, the kernel does grab as much memory as it can for buffers and cache, then 
release it on demands. All modern operating systems have done this for many 
years - Linux just doesn't try and hide that fact from you :-)

> I read on this list that the kernel needs *some* swap, even just a
> tiny amount, to function properly.  Is that true?  If so, do you think
> it would be OK to put this tiny amount of swap on a cheap SSD?

Not true. I have machines with zero swap and they work just fine. I am utterly 
unconcerned with out of memory conditions as whether you have swap or not, 
when virtual memory runs out, either way you have a horrible cockup that is 
hard to fix. Then there's the oom-killer that comes along, stomps all over 
everything and just makes it worse.

-- 
alan dot mckinnon at gmail dot com

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Grant]

>> OK, that's right.  How can I find out if 4GB RAM (the current amount)
>> is enough?  From what I understand of how Linux handles memory, it
>> will fill it up as quickly as possible, and then free it as necessary.
>>  This makes it difficult to determine how much RAM is necessary from
>> watching top.
>
> top lies. This has been discussed here many times. All your memory tools
> essentially tell you how much memory an app is able to see into, and most of
> that memory is shared with other stuff (like libs).
>
> You can't tell how much memory an app is using in any meaningful way, you are
> not supposed to even look at it as it changes millions of times a second. What
> you are supposed to do is select an allocation algorithm that works well for
> you in practice and let the kernel do the heavy lifting.
>
> Yes, the kernel does grab as much memory as it can for buffers and cache, then
> release it on demands. All modern operating systems have done this for many
> years - Linux just doesn't try and hide that fact from you :-)
>
>> I read on this list that the kernel needs *some* swap, even just a
>> tiny amount, to function properly.  Is that true?  If so, do you think
>> it would be OK to put this tiny amount of swap on a cheap SSD?
>
> Not true. I have machines with zero swap and they work just fine. I am utterly
> unconcerned with out of memory conditions as whether you have swap or not,
> when virtual memory runs out, either way you have a horrible cockup that is
> hard to fix. Then there's the oom-killer that comes along, stomps all over
> everything and just makes it worse.

Sounds good.  Will commenting the swap line out of /etc/fstab and
rebooting disable swap?  In order to resize the root partition to
include the swap paritition, I'll have to boot to LiveCD right?

- Grant

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Alex Schuster]

Grant writes:

> Sounds good.  Will commenting the swap line out of /etc/fstab and
> rebooting disable swap?

Yes. Or, temporarily,  the 'swapoff' command.

> In order to resize the root partition to
> include the swap paritition, I'll have to boot to LiveCD right?

I think it might work without. If you have hda1=boot, hda2=root, hda3=swap, 
you could delete hda3 and hda2 with [c]fdisk and make hda2 the size of 
hda2+hda3, then use resize2fs to increase the size of hda2. Increasing a 
file system's size works online nowadays. I don't think it would work with 
hda2=swap and hda3=root, but I'm not sure.

Using LVM, things would be easier :)

	Wonko

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Grant]

>> Sounds good.  Will commenting the swap line out of /etc/fstab and
>> rebooting disable swap?
>
> Yes. Or, temporarily,  the 'swapoff' command.
>
>> In order to resize the root partition to
>> include the swap paritition, I'll have to boot to LiveCD right?
>
> I think it might work without. If you have hda1=boot, hda2=root, hda3=swap,
> you could delete hda3 and hda2 with [c]fdisk and make hda2 the size of
> hda2+hda3, then use resize2fs to increase the size of hda2. Increasing a
> file system's size works online nowadays. I don't think it would work with
> hda2=swap and hda3=root, but I'm not sure.

Thanks everyone.

I have sda1=boot, sda2=swap, sda3=root.  Does anyone know if I'm
required to use a LiveCD in this case?

- Grant

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Alan McKinnon]

On Thursday 30 July 2009 17:45:30 Grant wrote:
> >> Sounds good.  Will commenting the swap line out of /etc/fstab and
> >> rebooting disable swap?
> >
> > Yes. Or, temporarily,  the 'swapoff' command.
> >
> >> In order to resize the root partition to
> >> include the swap paritition, I'll have to boot to LiveCD right?
> >
> > I think it might work without. If you have hda1=boot, hda2=root,
> > hda3=swap, you could delete hda3 and hda2 with [c]fdisk and make hda2 the
> > size of hda2+hda3, then use resize2fs to increase the size of hda2.
> > Increasing a file system's size works online nowadays. I don't think it
> > would work with hda2=swap and hda3=root, but I'm not sure.
>
> Thanks everyone.
>
> I have sda1=boot, sda2=swap, sda3=root.  Does anyone know if I'm
> required to use a LiveCD in this case?

Not only do you need a LiveCD, you need a backup and restore of your root 
partition. If you try and resize it from the front, you WILL LOSE THE 
FILESYSTEM ON IT.

Do this:

1. Backup /
2. Delete sda2 and sda3
3. Create a new sda2 the full size of the old sda2 and sda3 combined
4. Reorder partition table in fdsisk.
5. Fix entries in fstab from sda3 and higher.
6. REBOOT into LiveCD (or run partprobe if you aware of the effects)
7. mkfs sda2
8. Restore /
9. Reboot into main system

-- 
alan dot mckinnon at gmail dot com

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Alan McKinnon]

On Thursday 30 July 2009 15:47:18 Grant wrote:
> > Not true. I have machines with zero swap and they work just fine. I am
> > utterly unconcerned with out of memory conditions as whether you have
> > swap or not, when virtual memory runs out, either way you have a horrible
> > cockup that is hard to fix. Then there's the oom-killer that comes along,
> > stomps all over everything and just makes it worse.
>
> Sounds good.  Will commenting the swap line out of /etc/fstab and
> rebooting disable swap?  

Yes. Or you can just use swapoff as root.

> In order to resize the root partition to
> include the swap paritition, I'll have to boot to LiveCD right?

It's safest, but not always necessary.

If your partition table is laid out with the swap partition directly after the 
root partition, you can delete both, recreate the root partition the same size 
as both together. The new root partition must start where the old one did. 
Renumber the partitions and remember to adjust fstab if you mount by device 
number. Then resize the root file system. The filesystem and your kernel must 
support this.

If your root partition and swap partition are logical partitions in fdisk, 
this will probably fail. I do not know why, but I never got this to work. 
Physical partitions work just fine.

That's a lot of "ifs".

-- 
alan dot mckinnon at gmail dot com

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Neil Bothwick]

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On Thu, 30 Jul 2009 16:57:52 +0200, Alan McKinnon wrote:

> If your partition table is laid out with the swap partition directly
> after the root partition, you can delete both, recreate the root
> partition the same size as both together. The new root partition must
> start where the old one did. Renumber the partitions and remember to
> adjust fstab if you mount by device number. Then resize the root file
> system. The filesystem and your kernel must support this.
> 
> If your root partition and swap partition are logical partitions in
> fdisk, this will probably fail. I do not know why, but I never got this
> to work. 

I've done this with logical partitions, but I use cfdisk instead of fdisk.

It's moot anyway as Grant has swap before / so a live CD session with
gparted looks to be required.


-- 
Neil Bothwick

... Veni, Vidi, Visa - I came, I saw, I charged it.

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Re: [gentoo-user] {OT} SSD instead of RAID1?

[Peter Humphrey]

On Thursday 30 July 2009 14:47:18 Grant wrote:

> Sounds good.  Will commenting the swap line out of /etc/fstab and
> rebooting disable swap?

I'd also recompile the kernel with CONFIG_SWAP=n.

-- 
Rgds
Peter

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Alex Schuster]

Grant writes:

> From what I understand of how Linux handles memory, it
> will fill it up as quickly as possible, and then free it as necessary.
>  This makes it difficult to determine how much RAM is necessary from
> watching top.
>
> I read on this list that the kernel needs *some* swap, even just a
> tiny amount, to function properly.  Is that true?

Not really. Think about live-CDs, the usually do not use swap space.
However, I heard that having at least a little swap space may increase 
performance, regardless of how much free RAM there is. Don't know if this is 
still true nowadays (if it ever was), I doubt it.

> If so, do you think
> it would be OK to put this tiny amount of swap on a cheap SSD?

If you have enough RAM (with 4GB you probably have, but that depends on how 
you use your workstation), you can even put your swap into RAM. Sounds 
silly, but http://kerneltrap.org/node/3660 claims it makes some sense. I 
don't believe it, but I'm no expert.

	Wonko

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Paul Hartman]

On Thu, Jul 30, 2009 at 7:17 AM, Grant<emailgrant@gmail.com> wrote:
> I read on this list that the kernel needs *some* swap, even just a
> tiny amount, to function properly.  Is that true?  If so, do you think
> it would be OK to put this tiny amount of swap on a cheap SSD?

I have no swap and things work just fine. (8 gigs of RAM)

Obviously, running without swap increases the chances of you running
out of memory, but that has never happened to me.

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Grant]

>> I read on this list that the kernel needs *some* swap, even just a
>> tiny amount, to function properly.  Is that true?  If so, do you think
>> it would be OK to put this tiny amount of swap on a cheap SSD?
>
> I have no swap and things work just fine. (8 gigs of RAM)
>
> Obviously, running without swap increases the chances of you running
> out of memory, but that has never happened to me.

I've been setting up all of my systems according to this, creating a
512MB swap partition:

http://www.gentoo.org/doc/en/handbook/handbook-amd64.xml?part=1&chap=4

If I have 4GB RAM, all I'm accomplishing with swap is increasing this
to 4.5GB?  If my system requires 4.6GB at some point, I'm in the same
position I would be in if I had no swap and 4.1GB requirement?

- Grant

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Paul Hartman]

On Thu, Jul 30, 2009 at 11:03 AM, Grant<emailgrant@gmail.com> wrote:
>>> I read on this list that the kernel needs *some* swap, even just a
>>> tiny amount, to function properly.  Is that true?  If so, do you think
>>> it would be OK to put this tiny amount of swap on a cheap SSD?
>>
>> I have no swap and things work just fine. (8 gigs of RAM)
>>
>> Obviously, running without swap increases the chances of you running
>> out of memory, but that has never happened to me.
>
> I've been setting up all of my systems according to this, creating a
> 512MB swap partition:
>
> http://www.gentoo.org/doc/en/handbook/handbook-amd64.xml?part=1&chap=4
>
> If I have 4GB RAM, all I'm accomplishing with swap is increasing this
> to 4.5GB?  If my system requires 4.6GB at some point, I'm in the same
> position I would be in if I had no swap and 4.1GB requirement?

As far as I understand it, correct.

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Grant]

>>>> I read on this list that the kernel needs *some* swap, even just a
>>>> tiny amount, to function properly.  Is that true?  If so, do you think
>>>> it would be OK to put this tiny amount of swap on a cheap SSD?
>>>
>>> I have no swap and things work just fine. (8 gigs of RAM)
>>>
>>> Obviously, running without swap increases the chances of you running
>>> out of memory, but that has never happened to me.
>>
>> I've been setting up all of my systems according to this, creating a
>> 512MB swap partition:
>>
>> http://www.gentoo.org/doc/en/handbook/handbook-amd64.xml?part=1&chap=4
>>
>> If I have 4GB RAM, all I'm accomplishing with swap is increasing this
>> to 4.5GB?  If my system requires 4.6GB at some point, I'm in the same
>> position I would be in if I had no swap and 4.1GB requirement?
>
> As far as I understand it, correct.

Alright, I'm off swap for good then.  I love simplification.

- Grant

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Grant]

>>>> I read on this list that the kernel needs *some* swap, even just a
>>>> tiny amount, to function properly.  Is that true?  If so, do you think
>>>> it would be OK to put this tiny amount of swap on a cheap SSD?
>>>
>>> I have no swap and things work just fine. (8 gigs of RAM)
>>>
>>> Obviously, running without swap increases the chances of you running
>>> out of memory, but that has never happened to me.
>>
>> I've been setting up all of my systems according to this, creating a
>> 512MB swap partition:
>>
>> http://www.gentoo.org/doc/en/handbook/handbook-amd64.xml?part=1&chap=4
>>
>> If I have 4GB RAM, all I'm accomplishing with swap is increasing this
>> to 4.5GB?  If my system requires 4.6GB at some point, I'm in the same
>> position I would be in if I had no swap and 4.1GB requirement?
>
> As far as I understand it, correct.

What have you guys found to be the minimum RAM necessary for a Gentoo
system without swap that doesn't lock up?  My laptop has 1GB RAM and
512MB swap, and when I disabled the swap the system locked up during
the first big emerge.  I guess that means I need somewhere between 1GB
and 1.5GB.  I'd say it's a pretty normal laptop/workstation.

- Grant

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Neil Bothwick]

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On Wed, 29 Jul 2009 08:20:53 -0700, Grant wrote:

> Anyway, the point of all this is to prevent an HD failure from
> stopping the system.  An SSD is much safer, right?

SSDs are still relatively new technology, so predicting failure rates is
less reliable. What's wrong with using RAID-1? It's proven technology and
totally resistant to a single HD failure.


-- 
Neil Bothwick

Why do Kennedy's cry after sex? ..... Mace!

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Re: [gentoo-user] {OT} SSD instead of RAID1?

[Stroller]

On 29 Jul 2009, at 19:15, Neil Bothwick wrote:
> On Wed, 29 Jul 2009 08:20:53 -0700, Grant wrote:
>
>> Anyway, the point of all this is to prevent an HD failure from
>> stopping the system.  An SSD is much safer, right?
>
> SSDs are still relatively new technology, so predicting failure  
> rates is
> less reliable. What's wrong with using RAID-1? It's proven  
> technology and
> totally resistant to a single HD failure.

This was Grant's original question - whether SSD / flash technology is  
more reliable than RAID-1 of conventional disks? - and one to which no- 
one appeared comfortable giving a categorical answer.

Stroller.

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Grant]

>>> Anyway, the point of all this is to prevent an HD failure from
>>> stopping the system.  An SSD is much safer, right?
>>
>> SSDs are still relatively new technology, so predicting failure rates is
>> less reliable. What's wrong with using RAID-1? It's proven technology and
>> totally resistant to a single HD failure.
>
> This was Grant's original question - whether SSD / flash technology is more
> reliable than RAID-1 of conventional disks? - and one to which no-one
> appeared comfortable giving a categorical answer.
>
> Stroller.

I've come up with a couple reasons to wait a bit longer to switch my
important systems to SSD.

1. SLC is faster and (more importantly) should last much longer than
MLC.  The Super Talent Ultradrive 32GB drives are priced ~$120 for MLC
and ~$350 for SLC, so I'd like to wait for that SLC price to drop.
It's worth mentioning though, that even conservative estimates of MLC
lifetimes put them far beyond that of HD drives.

2. SSD fIrmware is being updated relatively frequently right now
(especially newer SSDs) and all data is lost during a firmware update.

I'm sold on SSDs as RAID1 replacements though.

BTW, I read that Samsung manufactures the memory for all major brand
SSDs (including Super Talent).

- Grant

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Grant]

>>>> Anyway, the point of all this is to prevent an HD failure from
>>>> stopping the system.  An SSD is much safer, right?
>>>
>>> SSDs are still relatively new technology, so predicting failure rates is
>>> less reliable. What's wrong with using RAID-1? It's proven technology and
>>> totally resistant to a single HD failure.
>>
>> This was Grant's original question - whether SSD / flash technology is more
>> reliable than RAID-1 of conventional disks? - and one to which no-one
>> appeared comfortable giving a categorical answer.
>>
>> Stroller.
>
> I've come up with a couple reasons to wait a bit longer to switch my
> important systems to SSD.
>
> 1. SLC is faster and (more importantly) should last much longer than
> MLC.  The Super Talent Ultradrive 32GB drives are priced ~$120 for MLC
> and ~$350 for SLC, so I'd like to wait for that SLC price to drop.
> It's worth mentioning though, that even conservative estimates of MLC
> lifetimes put them far beyond that of HD drives.
>
> 2. SSD fIrmware is being updated relatively frequently right now
> (especially newer SSDs) and all data is lost during a firmware update.
>
> I'm sold on SSDs as RAID1 replacements though.
>
> BTW, I read that Samsung manufactures the memory for all major brand
> SSDs (including Super Talent).
>
> - Grant

An interesting read here:

http://blogs.gentoo.org/nightmorph/2009/08/02/ssds-and-filesystems

- Grant

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Grant]

>> Anyway, the point of all this is to prevent an HD failure from
>> stopping the system.  An SSD is much safer, right?
>
> SSDs are still relatively new technology, so predicting failure rates is
> less reliable. What's wrong with using RAID-1? It's proven technology and
> totally resistant to a single HD failure.

Well, I've read great things about the reliability of SSDs.  Here's a
comment from Samsung:

http://www.engadget.com/2008/02/23/samsung-puts-the-kibosh-on-ssd-reliability-worries/

"a pattern could be perpetually repeated in which a 64GB SSD is
completely filled with data, erased, filled again, then erased again
every hour of every day for years, and the user still wouldn't reach
the theoretical write limit"

So in theory, the things are very reliable, but we wonder how they do
in the real world.

I'm considering a Super Talent Ultradrive which uses the relatively
new Indilinx controller.  There are 60 reviews of these drives on
newegg.com.  Of these 60, there are only 2 reports of operational
problems, most of the remainder are glowing tales of speed and
silence.  This is a "cheap" drive using technology that is new even
for an SSD, and still the newegg.com reports aren't dominated by
reports of "DOA!" or "Failed within 1 week!" like all of the
newegg.com HD reports I've seen.  Of course, this is far from
empirical evidence of SSD reliability, but it's very encouraging.

I shy away from RAID1 for a few reasons.  I posted these a little while ago:

1. RAID is another layer to learn, install, and maintain.

2. RAID isn't foolproof:

http://hardware.slashdot.org/article.pl?sid=08/10/21/2126252&from=rss
http://blogs.zdnet.com/storage/?p=162

3. RAID is relatively expensive on a hosted server.  Let's assume that
without RAID, the hard drive in use fails every 3 years and causes 24
hours of downtime with good backups.  That's a loss of .09% uptime
over 3 years.  If the server makes $100,000/year (and the same amount
every day), that's a loss of $273 over 3 years.  However, my host
wants $105/month for a second 15k hard drive and RAID controller card.
 The cost of that over 3 years is $3,780.

- Grant

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Stroller]

On 29 Jul 2009, at 16:20, Grant wrote:
> ...
> Anyway, the point of all this is to prevent an HD failure from
> stopping the system.  An SSD is much safer, right?

As I told you before, I used RAID-1 of two conventional olde spinning- 
platter hard-drives, using a hardware-RAID SATA controller. An  
additional drive can be standing by as a "hot-spare" or RAID6 can be  
used (on newer controllers) which resists failure of 2 drives per array.

Why would I mention this if flash memory is as "obviously" much safer  
as your above statement seems to imply?

Stroller.

Re: [gentoo-user] {OT} SSD instead of RAID1?

[Nevynxxx]

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Grant schrieb:
>> Aren't CF cards much slower than SSD drives and HD drives?
>>
>>     
How about using SD cards, like Dell/HP do in VMWare ESXi servers?

I'm just in th middle of speccig a server that will have zero local
storage, except the SD card that holds ESXi, all storage needs are
handled by iSCSI....

I'm not sure if SD would be faster/cheaper/better in any way, but they
sure are smaller!


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