Mailinglist Archive: opensuse-factory (648 mails)

[Greg Freemyer <greg.freemyer@xxxxxxxxx>]

On Mon, Nov 15, 2010 at 2:43 PM, Cristian Rodríguez
<crrodriguez@xxxxxxxxxxxx> wrote:
> El 15/11/10 13:09, Jeff Mahoney escribió:
>
>
> > - Batched discard support, which allows the file system to advise the
> >   block layer to use the TRIM command. This allows online TRIMs, but
> >   is only implemented in ext4 so far.
>
> Yeah, because in current kernel:head not even "discard" works see bnc#646863
>
> btw.. any hope of getting bnc#647554 fixed ?

Even in 2.6.37, it's a barely useful feature.

The ATA spec. allows for the TRIM command to have a payload of
numerous trim ranges.  The 2.6.37 ext4 kernel implementation only
sends one range at a time (except for very large ranges which are
broken into multiple contiguous ranges and sent in one TRIM payload).

Because TRIM causes the SSD to flush its cache, having one command per
range is still very ineffective, and the benchmarks show it is not a
major performance win.

OTOH, the userspace hdparm / wiper.sh pair do a great job and fully
leverage the multiple ranges per TRIM command.

Unfortunately, the hdparm / wiper.sh scripts don't support software
raid or LVM setups while the kernel implementation does.

So I would only advise using the kernel TRIM feature in those 2
limited environments.

See: http://en.opensuse.org/SDB:SSD_discard_%28trim%29_support

Greg
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