Hello, We have a medium-sized Ceph Luminous cluster that, up til now, has been the RBD image backend solely for an OpenStack Newton cluster that's marked for upgrade to Stein later this year. Recently we deployed a brand new Stein cluster however, and I'm curious whether the idea of pointing the new OpenStack cluster at the same RBD pools for Cinder/Glance/Nova as the Luminous cluster would be considered bad practice, or even potentially dangerous. One argument for doing it may be that multiple CInder/Glance/Nova pools serving disparate groups of clients would come at a PG cost to the cluster, though the separation of multiple, distinct pools also has its advantages. The UUIDs generated for RBD images in the pools by OpenStack services *should* be unique and collision-less between the 2 OpenStack clusters, in theory. One other point I was curious about was RBD image feature sets; Stein Ceph clients will be running later versions of Ceph libraries than Newton clients. If the 2 sets of clients were to share pools, would that itself cause problems (in the case that neither set needed to share RBD images within pools, only the pool itself) with some images in the pool having different feature lists? -- ******************* Paul Browne Research Computing Platforms University Information Services Roger Needham Building JJ Thompson Avenue University of Cambridge Cambridge United Kingdom E-Mail: pfb29(a)cam.ac.uk Tel: 0044-1223-746548 *******************