Dell NVMe issues

[Jim Harris]

On Tue, Oct 6, 2015 at 11:46 AM, Steven Hartland <killing at multiplay.co.uk>
wrote:

> On 06/10/2015 19:03, Jim Harris wrote:
>
>
>
> On Tue, Oct 6, 2015 at 9:42 AM, Steven Hartland <
> <killing at multiplay.co.uk>killing at multiplay.co.uk> wrote:
>
>> Also looks like nvme exposes a timeout_period sysctl you could try
>> increasing that as it could be too small for a full disk TRIM.
>>
>
>> Under CAM SCSI da support we have a delete_max which limits the max
>> single request size for a delete it may be we need something similar for
>> nvme as well to prevent this as it should still be chunking the deletes to
>> ensure this sort of thing doesn't happen.
>
>
> See attached.  Sean - can you try this patch with TRIM re-enabled in ZFS?
>
> I would be curious if TRIM passes without this patch if you increase the
> timeout_period as suggested.
>
> -Jim
>
>
> Interesting does the nvme spec not provide information from the device as
> to what its optimal / max deallocate request size should be like the ATA
> spec exposes?
>

Correct - there is no way for devices to specify a max/optimal deallocate
size in NVMe.  There is an implicit limit from the 32-bit LBA length in the
DSM Range data structure defined by the spec.  So this patch is needed
anyways to make sure we don't overflow the 32-bit LBA length.  Sean's
drives are 1.6TB which fits in an unsigned 32-bit value on a 512-byte
sector formatted controller, so I don't think that is the problem in Sean's
case.

-Jim



>     Regards
>     Steve
>