Re: [Scst-devel] Thin Provisioning and Ceph RBD's

[Vladislav B. <vs...@vl...>]

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.

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.

Vlad