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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
>
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