On 06/27/2017 06:24 AM, Wido den Hollander wrote:
Op 27 juni 2017 om 13:05 schreef Christian Balzer <chibi@xxxxxxx>:
On Tue, 27 Jun 2017 11:24:54 +0200 (CEST) Wido den Hollander wrote:
Hi,
I've been looking in the docs and the source code of BlueStore to figure out if it issues TRIM/Discard [0] on SSDs and I haven't been able to find an answer.
Does BlueStore/BlueFS issue these commands to give back the space to the underlying device?
For SSDs it improves both write performance and their lifespan, so it would be a very nice to have feature.
SATA 3.1 has "Queued TRIM Command" which allows it to be 'async' in the controller.
If it were that last bit, I'd be for it, if it isn't then something that
you can fully control akin to fstrim would be a much better idea.
Problem is that you can't run fstrim on BlueStore since it's not a mounted filesystem like XFS. Therefor TRIM/Discard would have to be issued by the OSD.
That being said, I'm disinclined to deploy any SSDs that actually REQUIRE
trim/discard to maintain their functional levels.
I wouldn't say require, but it never hurts to actually do a TRIM/Discard when it comes to the lifespan of a SSD.
However, I'm curious if this is actually in BlueStore or not.
FYI:
https://github.com/ceph/ceph/pull/14727
Wido
Christian
--
Christian Balzer Network/Systems Engineer
chibi@xxxxxxx Rakuten Communications
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