RADOS (Reliable Autonomic Distributed Object Store) is the heart of the Ceph storage system, which is also referred to as the Ceph storage cluster. RADOS provides all the precious features to Ceph, including distributed object store, high availability, reliablity, no single point of failure, self-healing, self-managing, and so on. As a result, the RADOS layer holds a special importance in the Ceph storage architecture. The data access methods of Ceph, such as RBD, CephFS, RADOSGW, and librados, all operate on top of the RADOS layer.

When the Ceph cluster receives a write request from clients, the CRUSH algorithm calculates the location and decides where the data should be written. This information is then passed to the RADOS layer for further processing. Based on the CRUSH ruleset, RADOS distributes the data to all the cluster nodes in the form of small objects. Finally, these objects are stored on OSDs.

RADOS, when configured with a replication factor of more than one, takes care...