The Ceph Storage Cluster has a messaging layer protocol that enables clients to interact with a Ceph Monitor and a Ceph OSD Daemon. librados provides this functionality to Ceph Clients in the form of a library. All Ceph Clients either use librados or the same functionality encapsulated in librados to interact with the object store. For example, librbd and libcephfs leverage this functionality. You may use librados to interact with Ceph directly (e.g., an application that talks to Ceph, your own interface to Ceph, etc.).