Comment 1 for bug 1387945

This is a VERY old and long running issue with how things work on the Nova side of the house. The volumes are going to get attached to the next available drive mapping (vdb, vdc, vdd) based on the Block Device Mapping table in Nova. The specification you provide to attach-volume is really more of a hint than anything else.

Anyway, over the past the answer has been "just use 'auto'" and save yourself the false sense of control here. Not acceptable for some, regardless this is a Nova operation and Cinder actually has no control or input here.

Marking invalid for Cinder and adding Nova.