I think that having a stand-alone  (client of cinder) rich data streaming
service (http put/get with offset support, which can be used for
conventional glance plus volume upload/download directly), and rich
data-source semantics exposed so that it can be used in an optimal way
by/for nova, need not wait on the cinder roadmap to be realised, and is
ultimately the right way to progress this.

Certain features may need to wait for cinder features (e.g. read-only
multi-attach is not available yet), but the basic framework could be
written right now, I think

On 19 November 2014 10:00, Flavio Percoco <fla...@redhat.com> wrote:

> On 19/11/14 15:21 +0800, henry hly wrote:
>
>> In the Previous BP [1], support for iscsi backend is introduced into
>> glance. However, it was abandoned because of Cinder backend
>> replacement.
>>
>> The reason is that all storage backend details should be hidden by
>> cinder, not exposed to other projects. However, with more and more
>> interest in "Converged Storage" like Ceph, it's necessary to expose
>> storage backend to glance as well as cinder.
>>
>> An example  is that when transferring bits between volume and image,
>> we can utilize advanced storage offload capability like linked clone
>> to do very fast instant copy. Maybe we need a more general glance
>> backend location support not only with iscsi.
>>
>>
>>
>> [1] https://blueprints.launchpad.net/glance/+spec/iscsi-backend-store
>>
>
> Hey Henry,
>
> This blueprint has been superseeded by one proposing a Cinder store
> for Glance. The Cinder store is, unfortunately, in a sorry state.
> Short story, it's not fully implemented.
>
> I truly think Glance is not the place where you'd have an iscsi store,
> that's Cinder's field and the best way to achieve what you want is by
> having a fully implemented Cinder store that doesn't rely on Cinder's
> API but has access to the volumes.
>
> Unfortunately, this is not possible now and I don't think it'll be
> possible until L (or even M?).
>
> FWIW, I think the use case you've mentioned is useful and it's
> something we have in our TODO list.
>
> Cheers,
> Flavio
>
> --
> @flaper87
> Flavio Percoco
>
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> OpenStack-dev@lists.openstack.org
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>
>


-- 
Duncan Thomas
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