John Griffith <[email protected]> wrote on 11/11/2012 17:01:37: > Hey Avishay, > > >>I guess I'm still confused about what a snapshot is > >>in OpenStack. Currently you can't really do anything with them via > >>OpenStack. > Sure you can, you can use them to create a new volume. They make a > good backup mechanism IMO.
Right - you can either make a new volume (=clone) or figure out somehow what name Cinder gave to the snapshot and make a backup on your own. [ Off topic question: How can a user determine the name of a volume/snapshot on the back-end for a given volume/snapshot? ] > I guess my question to you in your definition then is 'what's the > difference between a snapshot and a clone'? IMHO, a clone is a full, independent copy of the volume. It would copy all data (either in foreground or background) and leave the user with a volume - as if he created a new volume and used dd to copy all the data. A snapshot is something that depends on the original volume and in most implementations would contain only changed blocks. "Clone" definitely has other meanings - what's your definition? > Also, it Seems to me if we go with the idea of adding snapshot- > restore, and a true "clone" feature you get everything that you're > asking for here and more... so I'm not sure of the problem? Maybe > you could help me understand why defining snapshot and clone in the > manner described doesn't seem appropriate? So as I stated above, clone would give me a full copy, which can be wasteful. I should be able to read and write to snapshots within the context of Cinder. > FWIW, I think a R/O attach is something that would be good to have > as an option regardless. It's a necessity IMO. R/W is less common, but also very important. It's obvious that Cinder can't support features found in some storage controllers, but even LVM2 supports R/W snapshots (released almost 10 years ago). Don't get me wrong - LVM is awesome - but if ubiquitous, freely-available software supports a feature that controllers also generally support, I think Cinder should support it too. > Thanks, > John Thank you, Avishay _______________________________________________ Mailing list: https://launchpad.net/~openstack Post to : [email protected] Unsubscribe : https://launchpad.net/~openstack More help : https://help.launchpad.net/ListHelp
