[openstack-dev] Booting multiple instances with block device mapping
Vishvananda Ishaya
vishvananda at gmail.com
Thu Dec 13 01:15:34 UTC 2012
On Dec 12, 2012, at 3:45 PM, Caitlin Bestler <Caitlin.Bestler at nexenta.com> wrote:
>
>
> Phillip Pao wrote:
>
>> "it would be nice for cinder to have a concept of a read-only volume that could be attached to multiple instances"
>
> Or to be more precise, to be able to create thin volumes that overlayed a read-only base, where multiple instances
> could each reference their own overlay of the common read-only base.
We already have this. If you create a snapshot and boot from the snapshot it will create a volume from the snapshot and run that way. Some backends already support thin provisioning on the snapshot -> volume conversion.
A read-only volume is different and could be useful for different reasons. These include copy-on-write or copy-on-read on the connecting side as well as worker images that could have a read-only root filesystem and a scratch disk.
>
> Further, we should allow that reference image to be replicated, so as to allow the cloning to be done as close to the
> working VM as possible.
Replicating some "golden" images to multiple storage arrays also makes sense.
Vish
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