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From: Pasi Oja-Nisula on 5 Aug 2010 04:40
I have this:

Filesystem Size Used Avail Use% Mounted on
/dev/hda1 37G 14G 22G 39% /
tmpfs 3.9G 8.0K 3.9G 1% /lib/init/rw
udev 10M 640K 9.4M 7% /dev
tmpfs 3.9G 0 3.9G 0% /dev/shm
/dev/hda2 328G 204G 107G 66% /home
tmpfs 3.9G 49M 3.8G 2% /tmp
tmpfs 3.9G 0 3.9G 0% /var/lock
tmpfs 3.9G 296K 3.9G 1% /var/run
tmpfs 3.9G 32K 3.9G 1% /var/tmp
/dev/sdb1 917G 289G 582G 34% /root/backup

So basically I have root and home partitions and another disk
for backups of the whole thing.

Now I got a SSD disk, about which I don't really know much.
It's a 160 GB Intel, so it should be quite ok.
The question now is how to best utilize it in my configuration?
Or if I should just find other use for that?

I'm thinking for copying the whole root to SSD. Maybe have
40 GB partition for root and the rest for home. I have more stuff on
my home partition, but the active stuff is much less. So daily
used files would be on SSD and archive stuff on hard disk.

Should I worry about the longetivity of SSD? Maybe set noatime option,
but do I really need to deal with other filesystems than ext3? What about
/var/log and other places where there are lots of writing going on?

Pasi


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From: Jochen Schulz on 5 Aug 2010 05:30
Pasi Oja-Nisula:
>
> So basically I have root and home partitions and another disk
> for backups of the whole thing.
>
> Now I got a SSD disk, about which I don't really know much.
> It's a 160 GB Intel, so it should be quite ok.

"Quite ok" is "quite an understatement". :) Intel SSDs are still one of
the best choices in the market, as far as I know.

> I'm thinking for copying the whole root to SSD. Maybe have
> 40 GB partition for root and the rest for home. I have more stuff on
> my home partition, but the active stuff is much less. So daily
> used files would be on SSD and archive stuff on hard disk.

Sounds reasonable. You definitely should boot from the SSD and have all
your applications there. /home is not that important, but as there are
some applications that like writing to your $HOME a lot (Firefox, for
example), having it on your SSD helps performance, too. If you are
working with version control systems (svn, git, hg etc.) then you should
definitely put your repositories / working copies on the SSD.

> Should I worry about the longetivity of SSD?

Generally: no. Intel guarantees five years of 20GB writes per day:
http://download.intel.com/design/flash/nand/mainstream/mainstream-sata-ssd-datasheet.pdf

As long as you don't push HD movie files back and forth several times a
day, you don't need to worry. BTW, you can monitor lifetime writes with
recent kernels for each filesystem separately:

$ sudo tune2fs -l /dev/mapper/manowar-home-crypt | grep ^Lifet
Lifetime writes: 785 GB

This filesystem is almost exactly 13 months old and I think more than
half of the writes on my system go there. The rest is mostly package
upgrades (I am running sid).

What you might want to find out is whether you have a G1 or G2 device.
G2 supports the TRIM command which helps the SSD to keep up performance.
Otherwise, performance degrades over time, especially when you keep the
SSD nearly full. I have read Intel recommends keeping some of the space
(5-10%) unpartitioned in order to avoid that effect.

> Maybe set noatime option,

Good idea, but I do that even on traditional hard disks anyway. I am
using 'nodelalloc' on my ext4, too.

> but do I really need to deal with other filesystems than ext3?

Not really. I converted my /home to ext4, just to try it out, but I
don't really know what I gain from that. ;-)

> What about /var/log and other places where there are lots of writing
> going on?

Just don't care. A regular desktop system should only write a few
megabytes of logs per day. You might want to read Ted T'so's blog
entries regarding SSDs:
http://thunk.org/tytso/blog/category/computers/ssd/

J.
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From: Pasi Oja-Nisula on 6 Aug 2010 07:00
On Thu, Aug 5, 2010 at 11:27 PM, Jochen Schulz wrote:
> What you might want to find out is whether you have a G1 or G2 device.
> G2 supports the TRIM command which helps the SSD to keep up performance.
> Otherwise, performance degrades over time, especially when you keep the
> SSD nearly full. I have read Intel recommends keeping some of the space
> (5-10%) unpartitioned in order to avoid that effect.

Thanks Jochen. Lots of good information and pointers there. My SSD was actually
a G2 device. There was also newer firmware for the disk available
which I installed.

>> Maybe set noatime option,
>
> Good idea, but I do that even on traditional hard disks anyway. I am
> using 'nodelalloc' on my ext4, too.=20

Yes, I also found that I had noatime already on.

>> but do I really need to deal with other filesystems than ext3?
>
> Not really. I converted my /home to ext4, just to try it out, but I
> don't really know what I gain from that. ;-)

I haven't switched home yet, so I have only programs on SSD. But I
might also use ext4 for home.

> You might want to read Ted T'so's blog entries regarding SSDs:
> http://thunk.org/tytso/blog/category/computers/ssd/

This is where the pain starts. I started looking at this and suddenly I
was up to my neck in partition boundary alignment calculations. But
I guess I finally managed to get them right. Probably wouldn't have
made a difference even if I had skipped that part.

So far so good. Bigger programs like OpenOffice and the like start
noticeably quicker, but the difference is not as big as I thought. I'll
see how the system feels once I get home transferred also.

Pasi


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From: Jochen Schulz on 6 Aug 2010 15:20
Pasi Oja-Nisula:
> On Thu, Aug 5, 2010 at 11:27 PM, Jochen Schulz wrote:
>
>> You might want to read Ted T'so's blog entries regarding SSDs:
>> http://thunk.org/tytso/blog/category/computers/ssd/
>
> This is where the pain starts. I started looking at this and suddenly I
> was up to my neck in partition boundary alignment calculations. But
> I guess I finally managed to get them right. Probably wouldn't have
> made a difference even if I had skipped that part.

I skipped the alignment part completely and just went with the defaults
(from July 2009). I don't have the feeling that this imposes a
performance penalty like what is reported with the new 4k hard disks.
But I didn't test that.

> So far so good. Bigger programs like OpenOffice and the like start
> noticeably quicker, but the difference is not as big as I thought. I'll
> see how the system feels once I get home transferred also.

What about boot time? My laptop (Thinkpad X200) boots up in less than
ten senconds (boot manager to GDM).

J.
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[Agree] [Disagree]
<http://www.slowlydownward.com/NODATA/data_enter2.html>
From: Brian Ryans on 6 Aug 2010 15:20
Quoting Jochen Schulz on 2010-08-05 04:27:26:

> BTW, you can monitor lifetime writes with recent kernels for each
> filesystem separately:
>
> $ sudo tune2fs -l /dev/mapper/manowar-home-crypt | grep ^Lifet
> Lifetime writes: 785 GB
>
> This filesystem is almost exactly 13 months old and I think more than
> half of the writes on my system go there. The rest is mostly package
> upgrades (I am running sid).

Do you know what kernel exactly is required? My kernel isn't new
enough, or doesn't have the right options enabled, in order to show
this:

Linux esterhazy 2.6.26-2-686 #1 SMP Mon Jun 21 05:58:44 UTC 2010 i686 GNU/Linux

This is an up-to-date Lenny system.
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