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
replacing?
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
rebuild?
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?
-Ben
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