[openstack-dev] [nova] How should libvirt pools work with distributed storage drivers?

Peter Penchev openstack-dev at storpool.com
Wed Dec 17 08:44:06 UTC 2014

On Mon, Dec 1, 2014 at 9:52 PM, Solly Ross <sross at redhat.com> wrote:
> Hi Peter,
>> Right.  So just one more question now - seeing as the plan is to
>> deprecate non-libvirt-pool drivers in Kilo and then drop them entirely
>> in L, would it still make sense for me to submit a spec today for a
>> driver that would keep the images in our own proprietary distributed
>> storage format?  It would certainly seem to make sense for us and for
>> our customers right now and in the upcoming months - a bird in the
>> hand and so on; and we would certainly prefer it to be upstreamed in
>> OpenStack, since subclassing imagebackend.Backend is a bit difficult
>> right now without modifying the installed imagebackend.py (and of
>> course I meant Backend when I spoke about subclassing DiskImage in my
>> previous message).  So is there any chance that such a spec would be
>> accepted for Kilo?
> It doesn't hurt to try submitting a spec.  On the one hand, the driver
> would "come into life" (so to speak) as deprecated, which seems kind
> of silly (if there's no libvirt support at all for your driver, you
> couldn't just subclass the libvirt storage pool backend).  On the
> other hand, it's preferable to have code be upstream, and since you
> don't have a libvirt storage driver yet, the only way to have support
> is to use a legacy-style driver.

Thanks for the understanding!

> Personally, I wouldn't mind having a new legacy driver as long as
> you're committed to getting your storage driver into libvirt, so that
> we don't have to do extra work when the time comes to remove the legacy
> drivers.

Yes, that's very reasonable, and we are indeed committed to getting
our work into libvirt proper.

> If you do end up submitting a spec, keep in mind is that, for ease of
> migration to the libvirt storage pool driver, you should have volume names of
> '{instance_uuid}_{disk_name}' (similarly to the way that LVM does it).
> If you have a spec or some code, I'd be happy to give some feedback,
> if you'd like (post it on Gerrit as WIP, or something like that).

Well, I might have mentioned this earlier, seeing as the Kilo-1 spec
deadline is almost upon us, but the spec itself is at
https://review.openstack.org/137830/ - it would be great if you could
spare a minute to look at it.  Thanks in advance!


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