On 08/30/2013 02:22 PM, Oliver Daudey wrote:
Hey Mark,
On vr, 2013-08-30 at 13:04 -0500, Mark Chaney wrote:
Full disclosure, I have zero experience with openstack and ceph so far.
If I am going to use a Ceph RBD cluster to store my kvm instances, how
should I be doing backups?
1) I would prefer them to be incremental so that a whole backup doesnt
have to happen every night.
Others, correct me if I'm wrong, just starting to play with this feature
myself. :-)
You create a base-snapshot, which you re-create and back up, say, every
month and then you create another snapshot, say, every day. Ceph RBD
then allows you to generate a file with just the delta's between the two
snapshots. You back up those delta's and then either throw away the
daily snapshot, or keep it around for online restores, if you want. In
case of catastrophic failure of your RBD-pool, you first recover the
base-snapshots and then merge in the most recent daily delta's for that
month to get at your most recent state.
Yes, that's right. You may be interested in openstack cinder's backup
service as well, which recently got support for doing incremental
backups like this between ceph clusters [1]. In the future it could
potentially store the diffs somewhere else, instead of using a separate
ceph cluster.
Josh
[1] https://blueprints.launchpad.net/cinder/+spec/cinder-backup-to-ceph
See: http://ceph.com/dev-notes/incremental-snapshots-with-rbd/
2) I would also like the instances to obviously stay online during the
backup
No problem. Before starting your backup of an image, you first make a
snapshot of it and then backup the snapshot instead. Assuming you use a
journaled filesystem on your VMs, your general data should be consistent
in almost all cases. Specific applications, like databases, might still
not recover very well and may need to be put in a consistent state
within the VM before generating the snapshot. Snapshot-generation on
RBD is very fast and when finished, you can resume the VM and do your
backups off the snapshot. Test what happens if you try to restore and
use your backups. Regularly.. :-)
3) Backups will be stored off the ceph cluster on slower sata drives on
another storage server.
Sounds like a good idea. Store it off-site or at least in another
location in the building, if possible.
Regards,
Oliver
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