[openstack-dev] [Nova] Regarding deleting snapshot when instance is OFF

Eric Blake eblake at redhat.com
Wed Apr 8 22:52:23 UTC 2015

On 04/08/2015 12:01 PM, Deepak Shetty wrote:
> Questions:
> 1) Is this a valid scenario being tested ? Some say yes, I am not sure,
> since the test makes sure that instance is OFF before snap is deleted and
> this doesn't work for fs-backed drivers as they use hyp assisted snap which
> needs domain to be active.

Logically, it should be possible to delete snapshots when a domain is
off (qemu-img can do it, but libvirt has not yet been taught how to
manage it, in part because qemu-img is not as friendly as qemu in having
a re-connectible Unix socket monitor for tracking long-running progress).

> 2) If this is valid scenario, then it means libvirt.py in nova should be
> modified NOT to raise error, but continue with the snap delete (as if
> volume was not attached) and take care of the dom xml (so that domain is
> still bootable post snap deletion), is this the way to go ?

Obviously, it would be nice to get libvirt to support offline snapshot
deletion, but until then, upper layers will have to work around
libvirt's shortcomings.  I don't know if that helps answer your
questions, though.

Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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