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But the issue is, when told to detach, some of the drivers do bad things. then, is it the driver's issue to refcount to fix the issue, or is it nova's to refcount so that it doesn't call the release before all users are done with it? I think solving it in the middle, in cinder's probably not the right place to track it, but if its to be solved on nova's side, nova needs to know when it needs to do it. But cinder might have to relay some extra info from the backend.

Either way, On the driver side, there probably needs to be a mechanism on the driver to say it either can refcount properly so its multiattach compatible (or that nova should refcount), or to default to not allowing multiattach ever, so existing drivers don't break.

Thanks,
Kevin
________________________________________
From: Sean McGinnis [sean.mcginnis at gmx.com]
Sent: Wednesday, February 10, 2016 3:25 PM
To: OpenStack Development Mailing List (not for usage questions)
Subject: Re: [openstack-dev] [Nova][Cinder] Multi-attach, determining when to call os-brick's connector.disconnect_volume

On Wed, Feb 10, 2016 at 11:16:28PM +0000, Fox, Kevin M wrote:
> I think part of the issue is whether to count or not is cinder driver specific and only cinder knows if it should be done or not.
>
> But if cinder told nova that particular multiattach endpoints must be refcounted, that might resolve the issue?
>
> Thanks,
> Kevin

I this case (the point John and I were making at least) it doesn't
matter. Nothing is driver specific, so it wouldn't matter which backend
is being used.

If a volume is needed, request it to be attached. When it is no longer
needed, tell Cinder to take it away. Simple as that.


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