[openstack-dev] [nova][cinder] Nova is now using the Cinder volume attachments API - multiattach comes next

Melvin Hillsman mrhillsman at gmail.com
Sat Dec 9 20:13:52 UTC 2017

Great work and congratulations to everyone involved!

On Sat, Dec 9, 2017 at 1:15 PM, Matt Riedemann <mriedemos at gmail.com> wrote:

> I just wanted to take a minute to recognize that the patch [1] to make
> Nova use the new-style Cinder volume attach flow has merged.
> As one can tell from the patch set count alone, this has been in the works
> for a long time now.
> We were talking about volume multi-attach support back in Mitaka at the
> midcycle in Bristol. The early talks / patches would have piled more
> technical debt onto Nova and further baked in Nova's need to manage volume
> state, which is something we wanted to avoid, so at the Newton summit in
> Austin we changed course and decided to prioritize working on a new data
> model and API in Cinder, which eventually came out as the 3.27 volume
> attachments API in Ocata.
> There was then serious work on both sides in Pike to start using the new
> 3.27 API and we found out we needed some more changes to Cinder, which
> became the 3.44 Cinder API in Queens. Now Nova has merged the change at the
> end of a very long series of changes to enable the new flow once 3.44 is
> available to Nova and computes are all upgraded to understand the new flow.
> One can appreciate the complexity here if you read through the Nova spec
> for the new attach flow [2].
> I was really happy to see [1] merge this week because I knew we needed to
> get that in by the queens-2 milestone if we were going to have a shot at
> (1) flushing out stability issues before Queens RC1 and (2) a good chance
> to get multi-attach support into Nova in Queens.
> We have a plan for multi-attach support [3] which I think is doable before
> feature freeze. The Cinder 3.48 API is now available too which Nova needs
> to correctly detach a multi-attach volume.
> I want to thank everyone that's helped push this along for their
> dedication and patience, especially John Griffith, Ildiko Vancsa, Steve
> Noyes and John Garbutt. And thanks to Sean McGinnis, Jay Bryant, Walter
> Boring and Balazs Gibizer for review support.
> We've had weekly meetings between the Nova and Cinder teams for at least
> two years now and I can finally see the end so let's keep up the momentum.
> [1] https://review.openstack.org/#/c/330285/
> [2] https://specs.openstack.org/openstack/nova-specs/specs/queen
> s/approved/cinder-new-attach-apis.html
> [3] https://specs.openstack.org/openstack/nova-specs/specs/queen
> s/approved/cinder-volume-multi-attach.html
> --
> Thanks,
> Matt
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Kind regards,

Melvin Hillsman
mrhillsman at gmail.com
mobile: (832) 264-2646
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