Oh one final think - I'm unclear whether things like RBD have any implications on this. eg if we're using RBD for images, do we still have a local directory where we can store this info file ? I guess all RBD volumes are assumed to be raw by nova and we don't (currently) do anything stupid like storing a qcow2 file inside an RBD volume. Nice to have confirmation that this at least doesn't cause any problems for RBD and similar drivers.
Oh one final think - I'm unclear whether things like RBD have any implications on this. eg if we're using RBD for images, do we still have a local directory where we can store this info file ? I guess all RBD volumes are assumed to be raw by nova and we don't (currently) do anything stupid like storing a qcow2 file inside an RBD volume. Nice to have confirmation that this at least doesn't cause any problems for RBD and similar drivers.