Open Stack

Yeah, I think you are illustrating how this generates much confusion :)

To try to be more specific, the base functionality should be:

1. Create a point in time backup of a volume
2. Create a new volume from a backup (I guess it seems reasonable to
call this a clone)

This emulates the behavior of what EC2/EBS provide with volume
snapshots.  In this scenario, a "restore" is create a new volume from
the backup, and delete the old volume.

In the Storage world, much more can generally be done with snapshots.
For example in most storage system snapshots are treated just like a
normal volume and can be mounted directly.  A snapshot is often used
when creating a backup to ensure that you have a consistent point in
time backup, which I think most of the confusion comes from.

What we finally call it doesn't matter as much to me, as long as we
paint a consistent story that isn't confusing, and that we get it in
the Openstack API.

--
Chuck

On Wed, Jul 20, 2011 at 3:33 PM, Vishvananda Ishaya
<vishvananda at gmail.com> wrote:
> In rereading this i'm noticing that you are actually suggesting alternative usage:
>
> backup/clone
>
> snapshot/restore
>
> Correct?
>
> It seems like backup and snapshot are kind of interchangable.  This is quite confusing, perhaps we should refer to them as:
>
> partial-snapshot
>
> whole-snapshot
>
> or something along those lines that conveys that one is a differencing image and one is a copy of the entire object?
>
> On Jul 20, 2011, at 12:01 PM, Chuck Thier wrote:
>
>> At the last developers summit, it was noted by many, that the idea of
>> a volume snaphsot in the cloud is highly overloaded.  EBS uses the
>> notion of snapshots for making point in time backups of a volume that
>> can be used to create a new volume from.  These are not true snapshots
>> though from a storage world view.  Because of this I would like to
>> make the following proposal:
>>
>> Add a backup API to the Openstack API for Nova Volume.  This is to
>> provide EBS style snapshot functionality in the Openstack API.  I'm
>> proposing to name it backup instead of snapshot as that seems to
>> better describe what is happening.  It also allows room for other
>> storage backends to expose real snapshot capabilities down the road.
>>
>> In the case of Lunr, we would be making backups of volumes to swift
>> (possibly abstracted through glance in the future).
>>
>> I have started a blueprint and spec at:
>>
>> https://blueprints.launchpad.net/nova/+spec/backups-api
>> http://etherpad.openstack.org/volume-backup
>>
>> Please feel free to comment and contribute.
>>
>> --
>> Chuck
>>
>> _______________________________________________
>> Mailing list: https://launchpad.net/~openstack
>> Post to     : openstack at lists.launchpad.net
>> Unsubscribe : https://launchpad.net/~openstack
>> More help   : https://help.launchpad.net/ListHelp
>
>