Ceph monitors are responsible for monitoring the health of the entire cluster as well as maintaining the cluster membership state, state of peer nodes, and cluster configuration information. The Ceph monitor performs these tasks by maintaining a master copy of the cluster map. The cluster map includes Monitor maps, OSD maps, the PG map, the CRUSH map, and the MDS map. All these maps are collectively known as cluster maps. Let's take a quick look at the functionality of each map:
Monitor map: It holds end-to-end information about the monitor node, which includes the Ceph cluster id, monitor hostname, and IP address with the port number. It also stores the current epoch for map creation and last changed time too. You can check your cluster's monitor map by executing the following:
# ceph mon dumpOSD map: It stores some common fields, such as cluster ID, epoch for OSD map creation and last changed, and information related to pools, such as pool names, pool ID, type, replication...