Re: Tweaks for SSDs [Was: [gentoo-user] [ot] no more inodes]

[Eray Aslan <eray.aslan@caf.com.tr>]

On Sat, May 30, 2009 at 02:40:34PM +0100, Neil Bothwick wrote:
> On Sat, 30 May 2009 12:06:04 +0200, Florian Philipp wrote:
> 
> > Delaying commits with ext4 and/or laptop-mode will reduce the wear-down
> > of your SSD but it might as well freeze your system when the actual
> > commit takes place because these things tend to have a terribly low
> > write performance.
> 
> That may explain the pauses I get from time to time. Maybe shortening the
> commit period will help.

Couple of points regarding the pauses, SSDs, schedulers and ext3/ext4:

* try ext4 with its delayed allocation. It should help with pauses
* ext3 with data=writeback should help.  Some security implications with
data=writeback tho.  So be careful if it is not a single user machine.
* Deadline scheduler has more throughput than CFQ or anticipatory but it
is totally unusable under load
* A lot of patches to ext3 and ext4 for a/m pauses and SSDs.  Some made
it to kernel 2.6.30 I believe.
* Try CFQ and NOOP as schedulers for SSDs for now.  After the above
patches, CFQ should be the better choice.

Basically, a lot of changes to ext3/ext4 and schedulers at the moment.
I would wait for at least kernel 2.6.31 before trying alternatives and
making decisions.
 
> Or I could try btrfs, which has an ssd mount option.

Ugh.  Even on-disk format is not finalized yet.

-- 
Eray