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On Mon, May 13, 2013 at 9:47 PM, lzy.dev at gmail.com <lzy.dev at gmail.com>wrote:

> Hi, Guys
>
> Form below link, it seems Xen can support R/O volume attaching also:
> http://backdrift.org/xen-disk-hot-add-block-device-howto
>
> "xm block-attach <Domain> <BackDev> <FrontDev> <Mode> [BackDomain]"
> the "mode" can be R/O and R/W (r and w).
>
> Any thoughts? if not I will update the etherpad to adding xen.
>
> Thanks,
> Zhi Yan
>
> On Tue, May 14, 2013 at 2:26 AM, Martin, Kurt Frederick (ESSN Storage
> MSDU) <kurt.f.martin at hp.com> wrote:
> > Thanks Alessandro, I have also updated the etherpad
> > (
> https://etherpad.openstack.org/summit-havana-cinder-multi-attach-and-ro-volumes
> )
> > to include the latest findings regarding R/O volumes. It appears that a
> > number of hypervisors do indeed allow for setting the volumes to read
> only.
> >
> > Regards,
> >
> > Kurt Martin
> >
> >
> >
> > From: Alessandro Pilotti [mailto:ap at pilotti.it]
> > Sent: Monday, May 13, 2013 10:46 AM
> > To: OpenStack Development Mailing List
> > Subject: Re: [openstack-dev] [cinder] About Read-Only volume support
> > Importance: High
> >
> >
> >
> > Hi guys,
> >
> >
> >
> > "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".
> >
> >
> >
> > Hyper-V supports mounting R/O iSCSI volumes as well.
> >
> >
> >
> > Alessandro
> >
> >
> >
> >
> >
> > On May 13, 2013, at 13:22 , 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".
> >
> > 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.
> >
> > Thanks,
> > Zhi Yan
> >
> > _______________________________________________
> > OpenStack-dev mailing list
> > OpenStack-dev at lists.openstack.org
> > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
> >
> >
> >
> >
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> >
>
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Thanks Zhi Yan, I had some conversations with folks at the summit and the
general concensus seemed to be that it was possible.  There's a BP for this
that met a bit of objection:
https://blueprints.launchpad.net/cinder/+spec/shared-volume

perhaps we can work off of that and add some details to it.

Thanks,
John
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