Am 27.06.2017 um 13:05 schrieb Christian Balzer:
> 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.
> 
> That being said, I'm disinclined to deploy any SSDs that actually REQUIRE
> trim/discard to maintain their functional levels.

+1 All SSDs i've ever tested which require trim / discard to keep their
performance were unusable for something like ceph. Even it is async it
will bring extra load to the drive.

Stefan

> 
> Christian
> 
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