Best practices for SSD

[Chris Murphy]

On Feb 7, 2014, at 2:00 AM, sam tygier <samtygier at yahoo.co.uk> wrote:

> On 06/02/14 23:35, Chris Murphy wrote:
>> On Feb 6, 2014, at 7:43 AM, Wade Hampton <wadehamptoniv at gmail.com> wrote:
>>> - mount using discard (or use the fstrim program periodically)
>> 
>> The discard/TRIM debate can be found in the archives and also on devel@ archives, and on XFS archives. Not all SSDs perform that well with discard mount option because TRIM is a non-queued command, therefore for TRIM commands to be issued the drive cache must be cleared of all other commands and this can actually make things slower. So really it depends on your workload type, and the SSD you're using. I wouldn't assume you must have this enabled. Pretty much every source on this has been wrong, notable the crap resulting from coverage of Ubuntu moving to discard by default.
>> 
> 
> Ubuntu will be using a cronjob that calls fstrim, not the discard mount option. They found that the discard option cause a small performance hit.

Oops, that's right, thanks for the correction. I think they've gone with the better generic option using fstrim instead of discard: better in that it'll eventually get the SSD information on what blocks are no longer used by the file system, but also won't hang up certain SSDs that perform non-queued TRIM function slowly.

Chris Murphy