Open Stack

On 29 October 2013 04:20, Devananda van der Veen
<devananda.vdv at gmail.com> wrote:
> On Mon, Oct 28, 2013 at 6:35 AM, John Griffith <john.griffith at solidfire.com>
> wrote:

> I understand the desire to have something functional in nova-bm so you can
> iron out the other parts of the TripleO story that will rely on local data
> persisting through rebuild(). I think, as you pointed out, this would be
> pretty easy to do within the current nova-bm code. I guess I don't
> understand why using cinder volumes to act as the local non-ephemeral
> storage with libvirt is not sufficient...

Ah, because the short term TripleO will depend on the ephemeral
contract - that is that the hypervisor formats the device and that
cloud-init picks it up via nova metadata - via the block device
mapping subtree. If we use Cinder in virt and ephemeral in physical,
we now have a spurious testing difference that I'd like to avoid.

Emulated BM nodes will obviously not have such a difference, but it is
desirable to be able to test as much of the TripleO story as possible
on top of regular instances, because we can scale the quantity of
those /much/ more than either emulated BM nodes or physical nodes.

> Whether you're testing nova-bm on real or emulated hardware, the rebuild
> will be the same, and shouldn't use libvirt. The only reason I've thought of
> (in the last few minutes) why you'd need to change libvirt is if you're
> testing Heat and rebuild() without nova-bm, and you don't want divergent
> code (cinder with libvirt || no cinder with nova-bm). It actually makes more
> sense to me to test both code paths because the goal is to use cinder with
> Ironic, and so I *wouldn't* want to change the way libvirt does this today
> -- I would prefer to build the Ironic/Cinder/Nova-driver code to follow as
> many of the same code paths as possible.

So we should indeed test both code paths - once we have an Ironic
Cinder story, that needs to also be tested at both layers, and for
however long we support the [temporary] story with the ephemeral
partition we'll want to keep testing it as well.

> But you may have very different reasons that I'm overlooking, and I'm
> interested to hear them.

Nope, just testing layer consistency... though I say 'Just' and I mean
'this is super important for the ability to reason well about the
significance of test pass/fail'.

> Also, there will be a design session on Cinder for Ironic local storage:
>   http://summit.openstack.org/cfp/details/350


Cool.

-Rob


-- 
Robert Collins <rbtcollins at hp.com>
Distinguished Technologist
HP Converged Cloud