openstack team mailing list archive

[Chuck Thier <cthier@xxxxxxxxx>]

On Mon, May 2, 2011 at 2:45 PM, Eric Windisch <eric@xxxxxxxxxxxxxxxx> wrote:

>
> On May 2, 2011, at 12:50 PM, FUJITA Tomonori wrote:
>
> > Hello,
> >
> > Chuck told me at the conference that lunr team are still working on
> > the reference iSCSI target driver design and a possible design might
> > exploit device mapper snapshot feature.
>
> To clarify on the subject of snapshots: The naming of snapshots in Nova and
> their presence on disk is more confusing than it should be. There was some
> discussion of attempting to clarify the naming conventions.  Storage
> snapshots as provided by the device mapper are copy-on-write block devices,
> while Nova will also refer to file-backing stores as snapshots.  This latter
> definition is also used by EC2, but otherwise unknown and unused in the
> industry.
>

One of the things that was made very evident at the conference was the
confusion around snapshots in Lunr.  We were just talking about this in the
office, and we are considering renaming "snapshots" in the Lunr API to
"backups" to better indicate its intentions.  Backups will be made from a
volume, and a user will be able to create new volumes based on a backup.

This leads to another interesting question.  While our reference
implementation may not directly expose snapshot functionality, I imagine
other storage implementations could want to. I'm interested to hear what use
cases others would be interested in with snapshots.  The obvious ones are
things like creating a volume based on a snapshot, or rolling a volume back
to a previous snapshot.  I would like others' input here to shape what the
snapshot API might look like.

--
Chuck