> > In fact, I'm ok with delayed resize (upon power-cycle), and it's not an > issue for me that VM don't detect changes immediately. What I want to > understand is that changes to Cinder (and, thus, underlying changes to CEPH) > are safe for VM while it's in active state. > No, this is not considered safe. You are forcing the volume state to be availabile when it is in fact not. Not sure if it's an option for you, but in the Pike release support was added to be able to extend attached volumes. There are several caveats with this feature though. I believe it only works with libvirt, and if I remember right, only newer versions of libvirt. You need to have notifications working for Nova to pick up that Cinder has extended the volume. You can get some details from the cinder spec: https://specs.openstack.org/openstack/cinder-specs/specs/pike/extend-attached-volume.html And the corresponding Nova spec: http://specs.openstack.org/openstack/nova-specs/specs/pike/implemented/nova-support-attached-volume-extend.html You may also want to read through the mailing list thread if you want to get in to some of the nitty gritty details behind why certain design choices were made: http://lists.openstack.org/pipermail/openstack-dev/2017-April/115292.html