This came up in IRC today [1]. There are two issues: 1. As far as I can see, when creating a snapshot of a volume-backed server the API does not change the instance task_state so technically the user could perform some other action on the server while we're creating the volume snapshot(s), like try to resize it. My guess is that would fail since we likely can't be doing things like creating and deleting volume attachments on a volume that is actively being snapshot. 2. For image-backed servers, we set the progress the task_states through a few states [2] but those aren't conveyed in the overall server "status" field in the API [3]. Does anyone have any historical context on either of those issues? Issue #1 reminds me that we don't have a task_state transition while confirming a resized server either [4] but I guess that's less of an issue because there are not a lot of things you can do to a server in VERIFY_RESIZE status (delete and revert the resize I think), but that does mean I could fire off separate confirmResize and then revertResize actions on the same server at the same time and the confirm will probably fail down in compute rather than in the API with a 409 error. [1] http://eavesdrop.openstack.org/irclogs/%23openstack-nova/%23openstack-nova.2... [2] https://github.com/openstack/nova/blob/991d675675c1c6bb87a2b9d19327e2b4473f6... [3] https://github.com/openstack/nova/blob/991d675675c1c6bb87a2b9d19327e2b4473f6... [4] https://github.com/openstack/nova/blob/991d675675c1c6bb87a2b9d19327e2b4473f6... -- Thanks, Matt