The Ceph monitor does not store and serve data to clients; it serves updated cluster maps to clients as well as to other cluster nodes. Clients and other cluster nodes periodically check with monitors for the most recent copies of cluster maps. The Ceph monitor must be contacted by Ceph clients for obtaining the most recent copy of the cluster map before they can read or write data.
A Ceph storage cluster can operate with a single monitor, however, this introduces the risk of a single point of failure to the cluster; that is, if the monitor node goes down, Ceph clients cannot read or write data. To overcome this, a typical Ceph cluster consists of a cluster of Ceph monitors. A multi-monitored Ceph architecture develops quorum and provides consensus for distributed decision-making in clusters by using the Paxos algorithm. The monitor count in your cluster...