On Mon, 20 Oct 2014, Xavier Trilla wrote: > Hi, > > It seems Ceph doesn't allow rados pool snapshots on RBD pools which have or had RBD snapshots. They only work on RBD pools which never had a RBD snapshot. > > So, basically this works: > > rados mkpool test-pool 1024 1024 replicated > rbd -p test-pool create --size=102400 test-image > ceph osd pool mksnap test-pool rados-snap > > But this doesn't: > > rados mkpool test-pool 1024 1024 replicated > rbd -p test-pool create --size=102400 test-image > rbd -p test-pool snap create test-image@rbd-snap > ceph osd pool mksnap test-pool rados-snap > > And we get the following error message: > > Error EINVAL: pool test-pool is in unmanaged snaps mode > > I've been checking the source code and it seems to be the expecte behavior, but I did not manage to find any information regarding "unmanaged snaps mode". Also I did not find any information about RBD snapshots and pool snapshots being mutually exclusive. And even deleting all the RBD snapshots in a pool doesn't enable RADOS snapshots again. > > So, I have a couple of questions: > > - Are RBD and RADOS snapshots mutually exclusive? Xinxin already mentioned this, but to confirm, yes. > - What does mean "unmanaged snaps mode" message? It means the librados user is manaing its own snapshot metadata. I this case, that's RBD; it stores information about what snapshots apply to what images in the RBD header object. > - Is there any way to revert a pool status to allow RADOS pool snapshots after all RBD snapshots are removed? No. > We are designing a quite interesting way to perform incremental backups > of RBD pools managed by OpenStack Cinder. The idea is to do the > incremental backup at a RADOS level, basically using the mtime property > of the object and comparing it against the time we did the last backup / > pool snapshot. That way it should be really easy to find modified > objects transferring only them, making the implementation of a DR > solution easier.. But the issue explained here would be a big problem, > as the backup solution would stop working if just one user creates a RBD > snapshot on the pool (For example using Cinder Backup). This is already possible using the diff-export and diff-import functions of RBD on a per-image granularity. I think the only thing it doesn't provide is the ability to build a consistency group of lots of images and snapshot them together. Note also that listing all objects to find the changed ones is not very efficient. The export-diff function is currnetly also not very efficient (it enumerates image objects), but the 'object map' changes that Jason is working on for RBD will fix this and make it quite fast. sage > > I hope somebody could give us more information about this "unmanaged > snaps mode" or point us to a way to revert this behavior once all RBD > snapshots have been removed from a pool. > > Thanks! > > Saludos cordiales, > Xavier Trilla P. > Silicon Hosting > > ?Sab?as que ahora en SiliconHosting > resolvemos tus dudas t?cnicas gratis? > > M?s informaci?n en: siliconhosting.com/qa/ > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
 |