Open Stack

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