Hi Vlad,

On Wednesday, July 27, 2016, Vladislav Bolkhovitin <[email protected]> wrote:

>
> Alex Gorbachev wrote on 07/27/2016 10:33 AM:
> > One other experiment: just running blkdiscard against the RBD block
> > device completely clears it, to the point where the rbd-diff method
> > reports 0 blocks utilized.  So to summarize:
> >
> > - ESXi sending UNMAP via SCST does not seem to release storage from
> > RBD (BLOCKIO handler that is supposed to work with UNMAP)
> >
> > - blkdiscard does release the space
>
> How did you run blkdiscard? It might be that blkdiscard discarded big
> areas, while ESXi
> sending UNMAP commands for areas smaller, than min size, which could be
> discarded, or
> not aligned as needed, so those discard requests just ignored.


I indeed ran blkdiscard on the whole device.  So the question to the Ceph
list is below what length discard is ignored? I saw at least one other user
post a similar issue with ESXi-SCST-RBD.


>
> For completely correct test you need to run blkdiscard for exactly the
> same areas, both
> start and size, as the ESXi UNMAP requests you are seeing on the SCST
> traces.


I am running a test with the debug settings you provided, and will keep
this thread updated with results.  Much appreciate the guidance.

Alex


>
> Vlad
>
>

-- 
--
Alex Gorbachev
Storcium
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