Comment 9 for bug 1201418

I actually had a similar issue with a user having volumes attached to non-existent VMs.

I discovered that the user was using the not-so-well documented Cinder API call ``POST /volumes/{volume_id}/action`` through the python-cinderclient library. There are methods ``cinderclient.v{1,2}.volumes.VolumeManager.attach`` allowing a user to "set attachment metadata" without actually attaching volumes to instances.

To attach a volume to an instance in a Python script, one has to use the ``novaclient.v1_1.volumes.VolumeManager.create_server_volume`` method.

I wrote some documentation on that issue there: http://www.florentflament.com/blog/openstack-volume-in-use-although-vm-doesnt-exist.html