Comment 3 for bug 1335889

Initial analysis of Nova code is as follows.

The operation of deleting VM doesn't check if the VM is being attached with volume or not.
The operation of attaching volume to VM can't receive any status response from Cinder .

There is no sync between Nova and Cinder under this scenario.
Nova has no mechanism of pending an operation. Indeed, it just raises some Exception if invalid state is detected.
Cinder has no mechanism of responding the operation status.

Therefore, it's nearly impossible to resolve this problem completely. So, we ought to live with this problem.

A work-around is that Cinder should allow to delete an orphaned volume (i.e. the volume attached to an already-deleted VM).

Any feedback/comment is always appreciated