Live Migration [libvirt]/images_type=qcow2 to [libvirt]/images_type=rbd fails

[Henry Spanka]

Description
===========
Trying to migrate an instance from local storage to a hypervisor that is backed by RBD results in the error: invalid spec 'b05eafa0-e7da-4637-a47c-cddca5cc381c_/var/lib/nova/instances/b05eafa0-e7da-4637-a
47c-cddca5cc381c/disk'

Steps to reproduce
==================
* Create an instance from an image that is not on a rbd backend on a node that is configured to store the instance disk locally (as qcow2)
* Live-Migrate the instance to a node that is configured to use rbd as backend.
openstack server migrate --live compute-rbd --block-migration UUID

Expected result
===============
Migration completes successfully

Actual result
=============
rbd import command of base image fails with: Stderr: u"rbd: --pool is deprecated for import, use --dest-pool\nrbd: invalid spec 'b05eafa0-e7da-4637-a47c-cddca5cc381c_/var/lib/nova/instances/b05eafa0-e7da-4637-a
47c-cddca5cc381c/disk'\n"

The command run is: rbd import --pool vms /var/lib/nova/instances/_base/4d3facc86af22a33b3ca0eb95c1953c76b72bfaa b05eafa0-e7da-4637-a47c-cddca5cc381c_/var/lib/nova/instances/b05eafa0-e7da-4637-a47c-cddca5cc381c/disk --image-format=2 --id cinder --conf /etc/ceph/ceph.conf

A trace is attached below.

Environment
===========
Nova 10.1.0
CentOS 7.5
Ceph 12.2

Is there any way to migrate a local instance to a rbd backend or is this not supported?

[Henry Spanka (henryspanka)]

Added Trace

[Lee Yarwood (lyarwood)]

Moving between computes with different [libvirt]/images_types settings using live migration like this isn't supported. Additionally I don't believe cold migration between such computes would work either.

You should however be able to move these instances by creating a snapshot and recreating the instance on the new computes that are hopefully in a host aggregate separate to the original computes?

I'm going to mark this as opinion and wishlist to see if anyone thinks it's worth fixing this.