The sparseness is actually preserved, but the fast-diff stats are incorrect because zero-byte objects were being created during the flatten operation. This should be fixed under Luminous [1] where the flatten operation (and any writes to a clone more generally) no longer performs a zero-byte copy-up operation. The change was a little too invasive for comfort to backport to Jewel, however. [1] http://tracker.ceph.com/issues/15028 On Thu, Oct 12, 2017 at 5:06 PM, Massey, Kevin <kmassey@xxxxxxxxxx> wrote: > Hi, > > I'm evaluating ceph (Jewel) for an application that will have a chain of layered images, with the need to sometimes flatten from the top to limit chain length. However, it appears that running "rbd flatten" causes loss of sparseness in the clone. For example: > > $ rbd --version > ceph version 10.2.2 (45107e21c568dd033c2f0a3107dec8f0b0e58374) > $ rbd du > NAME PROVISIONED USED > child 10240k 0 > parent@snap 10240k 0 > parent 10240k 0 > <TOTAL> 20480k 0 > $ rbd info child > rbd image 'child': > size 10240 kB in 3 objects > order 22 (4096 kB objects) > block_name_prefix: rbd_data.18c852eb141f2 > format: 2 > features: layering, exclusive-lock, object-map, fast-diff, deep-flatten > flags: > parent: rbd/parent@snap > overlap: 10240 kB > $ rbd flatten child > Image flatten: 100% complete...done. > $ rbd du > NAME PROVISIONED USED > child 10240k 10240k > parent@snap 10240k 0 > parent 10240k 0 > <TOTAL> 20480k 10240k > > Is there any way to flatten a clone while retaining its sparseness, perhaps in Luminous or with BlueStore backend? > > Thanks, > Kevin > > > > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com -- Jason _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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