[openstack-dev] [nova] about rebuild instance booted from volume
openstack at nemebean.com
Thu Mar 15 14:27:55 UTC 2018
On 03/14/2018 08:46 AM, Matt Riedemann wrote:
> On 3/14/2018 3:42 AM, 李杰 wrote:
>> This is the spec about rebuild a instance booted from
>> volume.In the spec,there is a
>> question about if we should delete the old root_volume.Anyone
>> who is interested in
>> booted from volume can help to review this. Any suggestion is
>> welcome.Thank you!
>> The link is here.
>> Re:the rebuild spec:https://review.openstack.org/#/c/532407/
> Copying the operators list and giving some more context.
> This spec is proposing to add support for rebuild with a new image for
> volume-backed servers, which today is just a 400 failure in the API
> since the compute doesn't support that scenario.
> With the proposed solution, the backing root volume would be deleted and
> a new volume would be created from the new image, similar to how boot
> from volume works.
> The question raised in the spec is whether or not nova should delete the
> root volume even if its delete_on_termination flag is set to False. The
> semantics get a bit weird here since that flag was not meant for this
> scenario, it's meant to be used when deleting the server to which the
> volume is attached. Rebuilding a server is not deleting it, but we would
> need to replace the root volume, so what do we do with the volume we're
> Do we say that delete_on_termination only applies to deleting a server
> and not rebuild and therefore nova can delete the root volume during a
> If we don't delete the volume during rebuild, we could end up leaving a
> lot of volumes lying around that the user then has to clean up,
> otherwise they'll eventually go over quota.
> We need user (and operator) feedback on this issue and what they would
> expect to happen.
As a developer who would also be a user of this functionality, I don't
want the volume left around after rebuild. To me the data loss of the
root disk is inherent in the rebuild operation. I guess the one gotcha
might be that I always create the root volume as part of the initial
instance creation, if someone manually created a volume and then pointed
Nova at it there's probably a better chance they don't want Nova to
delete it on them.
Rather than overload delete_on_termination, could another flag like
delete_on_rebuild be added?
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