[ltp] SSD optimisation

[Marius Gedminas]

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On Thu, Jan 13, 2011 at 11:45:03AM +0100, Leon Brokken wrote:
> On 01/13/2011 10:02 AM, Tino Keitel wrote:
> > On Tue, Jan 11, 2011 at 21:12:12 -0500, Dan M. wrote:
> >> If your distro supports trim and your ssd has poor garbage collection
> >> I would suggest the discard option in your /etc/fstab in order to use
> >> the kernel trim feature.
> > AFAIK this requires a 2.6.36 kernel if used together with LVM.=20
> > Otherwise the filesystem won't be able to send a discard command to the
> > device. If the distribution uses an older kernel, trim won't work on
> > LVM.
> Thanks for the replies.
>=20
> I'm running an up to date kernel. Would you recommend to use LVM on the
> Intel SSD to benefit from trim?

LVM is not necessary for trim support.

LVM is a layer between the filesystem and the disk, so it needs to
explicitly support passing trim commands from the filesystem to the
lower level.  Apparently it gained this support in 2.6.36.

If you've no plans to use LVM, you can use an older kernel and benefit
=66rom trim.

> I have no idea about "garbage
> collection" on this disk.

Intel SSDs are said to be among the best.

AnandTech reviews of older models of Intel SSDs reported a certain
performance degradation (30%? I don't remember) once the filesystem
filled up, compared to performance when the disk was fresh.  Trim helps
avoid that.  (Then again 30% off light speed is still miles ahead of
rotational hard drives, if I you'll excuse my mixed metaphors.)

Marius Gedminas
--=20
IBM motto: "If you can't read our assembly language, you must be
borderline dyslexic, and we don't want you to mess with it anyway"
		-- Linus Torvalds

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