[openstack-dev] [Cinder] A possible solution for HA Active-Active

Gorka Eguileor geguileo at redhat.com
Sun Aug 2 22:49:46 UTC 2015


On Fri, Jul 31, 2015 at 01:47:22AM -0700, Mike Perez wrote:
> On Mon, Jul 27, 2015 at 12:35 PM, Gorka Eguileor <geguileo at redhat.com> wrote:
> > I know we've all been looking at the HA Active-Active problem in Cinder
> > and trying our best to figure out possible solutions to the different
> > issues, and since current plan is going to take a while (because it
> > requires that we finish first fixing Cinder-Nova interactions), I've been
> > looking at alternatives that allow Active-Active configurations without
> > needing to wait for those changes to take effect.
> >
> > And I think I have found a possible solution, but since the HA A-A
> > problem has a lot of moving parts I ended up upgrading my initial
> > Etherpad notes to a post [1].
> >
> > Even if we decide that this is not the way to go, which we'll probably
> > do, I still think that the post brings a little clarity on all the
> > moving parts of the problem, even some that are not reflected on our
> > Etherpad [2], and it can help us not miss anything when deciding on a
> > different solution.
> 
> Based on IRC conversations in the Cinder room and hearing people's
> opinions in the spec reviews, I'm not convinced the complexity that a
> distributed lock manager adds to Cinder for both developers and the
> operators who ultimately are going to have to learn to maintain things
> like Zoo Keeper as a result is worth it.
> 
> **Key point**: We're not scaling Cinder itself, it's about scaling to
> avoid build up of operations from the storage backend solutions
> themselves.
> 
> Whatever people think ZooKeeper "scaling level" is going to accomplish
> is not even a question. We don't need it, because Cinder isn't as
> complex as people are making it.
> 
> I'd like to think the Cinder team is a great in recognizing potential
> cross project initiatives. Look at what Thang Pham has done with
> Nova's version object solution. He made a generic solution into an
> Oslo solution for all, and Cinder is using it. That was awesome, and
> people really appreciated that there was a focus for other projects to
> get better, not just Cinder.
> 
> Have people consider Ironic's hash ring solution? The project Akanda
> is now adopting it [1], and I think it might have potential. I'd
> appreciate it if interested parties could have this evaluated before
> the Cinder midcycle sprint next week, to be ready for discussion.
> 
> [1] - https://review.openstack.org/#/c/195366/
> 
> -- Mike Perez

Hi all,

Since my original proposal was more complex that it needed be I have a
new proposal of a simpler solution, and I describe how we can do it with
or without a DLM since we don't seem to reach an agreement on that.

The solution description was more rushed than previous one so I may have
missed some things.

http://gorka.eguileor.com/simpler-road-to-cinder-active-active/

Cheers,
Gorka.




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