Hi! I'm new with ceph and i struggle to make a mapping between my current storage knowledge and ceph... So, i will state my understanding of the context and the question so please correct me with anything that i got wrong :) So, files (or pieces of files) are put in PGs that are given sections of OSDs. The crushmap gives a physical OSDs map to be chosen for placement or access Pools are a logical name for a storage space but how can i specify what osds or host are part of a pool? For replication, how can i specify: if a replica is missing (for a given time) start rebuilding on some available OSD? Is there a notion of "spare" so if an osd is missing on action, the rebuild to start on another host and when the old OSD is back (the hdd is replaced, or the machine was repaired) to be automatically cleaned up and used? I'm thinking about a 3 node cluster with the replica=2 failure domain = host, in such a way if one node is down, the data from there to be replicated on the remaining nodes (with some drives kept as spares..) I am almost certain that from the point of view of ceph, what i'm thinking is wrong so i would love to receive some advice :) Thanks a lot! Adrian