Open Stack

On Mon, May 13, 2013 at 4:22 AM, lzy.dev at gmail.com <lzy.dev at gmail.com>wrote:

> Hi All,
>
> In
> https://etherpad.openstack.org/summit-havana-cinder-multi-attach-and-ro-volumes
> ,
> I saw a comment there:
> "Summit feedback: Not doing R/O volumes due to the limited hypervisor
> that can support setting the volume to R/O, currently only KVM has
> this capability".
>
There was some disagreement in the group around this which you read on the
etherpad, however IMO
after talking to some folks with more Hypervisor experience/knowledge than
myself I don't think some of the
concerns that were voice were completely accurate.


>
> I agree there probably have some troubles cause R/O volumes support
> hard to implement.
> But maybe since I have not attended the summit, nova and cinder guys
> not notice there is a blueprint to plan to implement a cinder backend
> driver for glance
> (https://blueprints.launchpad.net/glance/+spec/glance-cinder-driver, I
> proposed), so I consider the R/O volumes support can be implemented
> gracefully.
> Under the case, the R/O volume stored in cinder will be created as an
> image, client can access it by glance via standard api, and nova can
> prepare the R/W image (base on R/O volume) for the instance normally.
>
> And more, I consider the R/O volume support and cinder driver for
> glance is valuable  because on nova side we can give some code changes
> to allow nova prepare instance disk via particular COW mechanism base
> on particular cinder backend store capability with more efficiency
> way, such as efficient snapshot.
>
> So the use cases you point out are exactly the types of things on my list
when I was thinking about this, and I think there are other benefits as
well.  I've met some resistance on this but my plan is that if I have time
later in the cycle to bring the bp back online and work on it I fully
intend to do so.


> Thanks,
> Zhi Yan
>

Thanks for the feed-back Zhi Yan.
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