[Openstack-operators] [openstack-dev] [nova] about rebuild instance booted from volume

Matt Riedemann mriedemos at gmail.com
Wed Mar 14 13:46:41 UTC 2018

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.




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