[ceph-users] Building a petabyte cluster from scratch

Hi Ceph users ! After years of using Ceph, we plan to build soon a new cluster bigger than what we've done in the past. As the project is still in reflection, I'd like to have your thoughts on our planned design : any feedback is welcome :) ## Requirements * ~1 PB usable space for file storage, extensible in the future * The files are mostly "hot" data, no cold storage * Purpose : storage for big files being essentially used on windows workstations (10G access) * Performance is better :) ## Global design * 8+3 Erasure Coded pool * ZFS on RBD, exposed via samba shares (cluster with failover) ## Hardware * 1 rack (multi-site would be better, of course...) * OSD nodes : 14 x supermicro servers * 24 usable bays in 2U rackspace * 16 x 10 TB nearline SAS HDD (8 bays for future needs) * 2 x Xeon Silver 4212 (12C/24T) * 128 GB RAM * 4 x 40G QSFP+ * Networking : 2 x Cisco N3K 3132Q or 3164Q * 2 x 40G per server for ceph network (LACP/VPC for HA) * 2 x 40G per server for public network (LACP/VPC for HA) * QSFP+ DAC cables ## Sizing If we've done the maths well, we expect to have : * 2.24 PB of raw storage, extensible to 3.36 PB by adding HDD * 1.63 PB expected usable space with 8+3 EC, extensible to 2.44 PB * ~1 PB of usable space if we want to keep the OSD use under 66% to allow loosing nodes without problem, extensible to 1.6 PB (same condition) ## Reflections * We're used to run mons and mgrs daemons on a few of our OSD nodes, without any issue so far : is this a bad idea for a big cluster ? * We thought using cache tiering on an SSD pool, but a large part of the PB is used on a daily basis, so we expect the cache to be not so effective and really expensive ? * Could a 2x10G network be enough ? * ZFS on Ceph ? Any thoughts ? * What about CephFS ? We'd like to use RBD diff for backups but it looks impossible to use snapshot diff with Cephfs ? Thanks for reading, and sharing your experiences ! F.