There is a regression in librbd in v0.94.4 that can cause VMs to crash. For now, please refrain from upgrading hypervisor nodes or other librbd users to v0.94.4. http://tracker.ceph.com/issues/13559 The problem does not affect server-side daemons (ceph-mon, ceph-osd, etc.). Jason's identified the bug and has a fix prepared, but it'll probably take a few days before we have v0.94.5 out. https://github.com/ceph/ceph/commit/4692c330bd992a06b97b5b8975ab71952b22477a Thanks! sage