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

[Alex G. <ag...@is...>]

Hi Nick, Vlad, SCST Team,

>> > I have been looking at using the rbd-nbd tool, so that the caching is
>> provided by librbd and then use BLOCKIO with SCST. This will however need
>> some work on the SCST resource agents to ensure the librbd cache is
>> invalidated on ALUA state change.
>> >
>> > The other thing I have seen is this
>> >
>> > https://lwn.net/Articles/691871/
>> >
>> > Which may mean FILEIO will support thin provisioning sometime in the
>> future???

I have run this configuration (RBD with BLOCKIO via SCST) through
VMWare's UNMAP test.  Basically, it runs:

esxcli storage vmfs unmap -l <datastore>

But the space is not reclaimed from RBD device, as is easily seen
polling the actual use (using method in
http://ceph.com/planet/real-size-of-a-ceph-rbd-image/)

SCST thin_provisioned attribute in sysfs is showing 1

Something appears to not be connecting the reclaim action.

Thank you,
Alex