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Old 08-05-2010, 08:15 AM
Pasi Oja-Nisula
 
Default What to put on SSD

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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Old 08-05-2010, 09:27 AM
Jochen Schulz
 
Default What to put on SSD

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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Old 08-06-2010, 06:22 AM
Brian Ryans
 
Default What to put on SSD

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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Old 08-06-2010, 10:39 AM
Pasi Oja-Nisula
 
Default What to put on SSD

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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Old 08-06-2010, 07:14 PM
Jochen Schulz
 
Default What to put on SSD

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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Old 08-06-2010, 09:24 PM
Jochen Schulz
 
Default What to put on SSD

Brian Ryans:
> 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?

Sorry, no. I usually run current sid and compile vanilla kernels from
Linus' git. This is supported by upstream since at least July 2009, so I
guess 2.6.30 or 2.6.31 should be enough. But I cannot find any
references regarding that.

What I just found out, though, is that the X25m apparently reports host
writes as S.M.A.R.T. attribute 225:

$ sudo smartctl -a /dev/sda | grep ^225
225 Host_Writes_Count 0x0000 200 200 000 Old_age Offline - 53426

http://www.spinics.net/lists/linux-ext4/msg19641.html

The raw value multiplied by 32MB is supposed to be the total amount of
data written to the device during its total lifetime. That's about
1,700GB for me which appears to be plausible (and only 4% of the writes
Intel reports as minimum lifetime writes).

J.
--
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up leading the hypnotised.
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Old 08-09-2010, 09:08 AM
Andrei Popescu
 
Default What to put on SSD

On Vi, 06 aug 10, 21:14:21, Jochen Schulz wrote:
>
> What about boot time? My laptop (Thinkpad X200) boots up in less than
> ten senconds (boot manager to GDM).

Are you using anything special besides the (now default) parallel boot?
I'm thinking about readahead or similar stuff.

Regards,
Andrei
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Old 08-09-2010, 10:47 PM
Jochen Schulz
 
Default What to put on SSD

[Re-posted to the list]

Andrei Popescu:
> On Vi, 06 aug 10, 21:14:21, Jochen Schulz wrote:
>>
>> What about boot time? My laptop (Thinkpad X200) boots up in less than
>> ten senconds (boot manager to GDM).
>
> Are you using anything special besides the (now default) parallel boot?
> I'm thinking about readahead or similar stuff.

No, just the current defaults in sid. What services are started can be
seen here (vertical lines drawn each second):

http://well-adjusted.de/~jrschulz/gfx/bootchart-2010-03-26.png

Total boot time is about 30-35 seconds, depending on how fast I enter my
disk encryption + login passwords. For chart rendering, I have
temporarily disabled my encrypted /home.

I don't use any of the big desktop environments, just plain awesome (the
window manager). But that isn't included in the chart anyway.

BTW, I tried slim instead of gdm, but I found it to be a little bit on
the buggy side and IIRC it lacks a few features I like (don't remember
which).

J.
--
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[Agree] [Disagree]
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Old 08-10-2010, 02:04 AM
Celejar
 
Default What to put on SSD

On Tue, 10 Aug 2010 00:47:02 +0200
Jochen Schulz <ml@well-adjusted.de> wrote:

...

> Total boot time is about 30-35 seconds, depending on how fast I enter my
> disk encryption + login passwords. For chart rendering, I have
> temporarily disabled my encrypted /home.

When I switched over to full-disk encryption, I decided that I didn't
really need two passwords, and I ditched the login password by using
rungetty with the --autologin option.

Celejar
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Old 08-13-2010, 03:31 PM
Jörg-Volker Peetz
 
Default What to put on SSD

Did you enable the 'discard' mount option on your ext4 file system (see
kernel-/Documentation/filesystems/ext4.txt) in order to make usage of
the TRIM-ability of the SSD?
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