The core storage layer in Ceph is the Reliable Autonomous Distributed Object Store (RADOS), which, as the name suggests, provides an object store on which the higher-level storage protocols are built. The RADOS layer in Ceph consists of a number of object storage daemons (OSDs). Each OSD is completely independent and forms peer-to-peer relationships to form a cluster. Each OSD is typically mapped to a single disk, in contrast to the traditional approach of presenting a number of disks combined into a single device via a RAID controller to the OS.

The other key component in a Ceph cluster is the monitors. These are responsible for forming a cluster quorum via the use of Paxos. The monitors are not directly involved in the data path and do not have the same performance requirements of OSDs. They are mainly used to provide a known cluster state, including membership...