Open Stack

On Wed, Oct 30, 2013 at 04:20:34AM -0400, Russell Bryant wrote:
> On 10/30/2013 03:13 AM, Alex Glikson wrote:
> > Maybe a more appropriate approach could be to have a tool/script that
> > does it, as a one time thing.
> > For example, it could make sense in a scenario when Nova DB gets lost or
> > corrupted, a new Nova controller is deployed, and the DB needs to be
> > recreated. Potentially, since Nova DB is primarily a cache, this could
> > be done by 'discovery' (maybe with some manual intervention) - instead
> > of dealing with backup/restore of the DB, or similar approaches.
> 
> The need for this sort of thing makes more sense for traditional
> datacenter virtualization, but not as much for cloud.  That's the root
> of my objection.

I'm not sure I agree with this distinction. I think that in cloud
individual VMs, and even individual virt hosts, are fine to be
considered disposable assets. I don't think I'd consider the entire
cloud deployment to be disposable - which is what we're talking about
if we consider the "DB lost" disaster scenario. Yes, you may loose
an entire deployment, but I think you'd want todo as much as is
reasonable possible to avoid that scenario because it could be very
costly to have a complete outage like that. Perhaps you'd argue that
they should use cells, and that individual cells should be considered
to be completely disposable still ? At some point though I think you
get to a scale where some disaster recovery is needed.

That all said, in the "DB lost" scenario, I think that detecting and
reconnecting to VMs is the least of the problems, and certainly not
the first thing you'd need to attack. You need to know who owns what
assets, otherwise you'll never be able to allow users access to their
VMs again. If that ownership data was in the DB that was lost, then
everything else is somewhat academic until that problem is solved.
This is somewhat digressing though, since the original blueprint
mentioned in this thread was not about disaster recovery processes.

Regards,
Daniel
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org       -o-       http://live.gnome.org/gtk-vnc :|