Comment 16 for bug 1578036

I stumbled over this issue today. In mitaka there are actually 3 related issues which prevent differential backups for Ceph from working:

* https://review.openstack.org/#/c/326696/ fixed the detection of RBD volumes and is fixed in Newton.

Once this issue is fixed, differential backups of volumes which are in state 'available' work. For volumes which are in-use the issue from comment #5 appears. This is because in CephBackupDriver.backup tries to get the id and name rbd image name of the volume by querying the database for the original volume to backup. But since change
https://review.openstack.org/#/c/262395/ the original volume is cloned if it's in use and a backup of the cloned volume is taken. When calling rbd export-diff the ceph driver mixes up this cloned volume and the original volume.

The third issue is not directly related to this bug:

* https://review.openstack.org/#/c/378945/ prevents leaving all connections to the Ceph cluster open