[Openstack] Root disks with Ceph

Greg Chavez greg.chavez at gmail.com
Wed Sep 11 18:39:29 UTC 2013

John: I'm talking about primary root disk storage.  Secondary storage would
persist of course.

Mike: Right, I just want to establish that if I set the default Cinder
plugin to RBD volumes, and I do nothing else, root volumes are ephemeral.
 That seems to be the case anyway.

Seems like some of these parameters become meaningless depending on your
backing store.  As another example, do you really need to specify a root
disk parameter if you're booting from a volume?  I would think not.

Thanks for your responses.

On Wed, Sep 11, 2013 at 1:29 PM, Mike Dawson <mike.dawson at cloudapt.com>wrote:

> When you create an instance backed by an RBD Cinder volume, you can
> specify which behavior you want. There is a check box in Horizon to toggle
> the behavior.
> Thanks,
> Mike Dawson
> On 9/11/2013 1:15 PM, Greg Chavez wrote:
>> So if I use RBD as my storage backend for Cinder, what happens to the
>> root disks of VMs that I terminate?
>> Do they still exist as RBD volumes in Ceph or are they
>> deleted/marked-as-free?
>> If the answer is that they get deleted, or at the very least OpenStack
>> no longer keeps track of them, then there isn't much difference between
>> the root and ephemeral disks in the flavors I am using. other than their
>> being distinct disk devices.  Or so it seems to me.

--Greg Chavez
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