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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<mailto: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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