Object storage cannot be directly accessed by an operating system as a disk of a filesystem. Rather, it can only be accessed via API at the application level. Ceph is a distributed object storage system that provides an object storage interface via the Ceph object gateway, also known as the RADOS Gateway (RGW) interface, which has been built on top of the Ceph RADOS layer. The RGW uses librgw (RADOS Gateway Library) and librados, allowing applications to establish a connection with the Ceph object storage. The RGW provides applications with a RESTful S3 / Swift-compatible API interface to store data in the form of objects in the Ceph cluster. Ceph also supports multitenant object storage, accessible via RESTful API. In addition to this, the RGW also supports Ceph Admin APIs that can be used to manage the Ceph storage cluster using native API calls.

The librados software libraries are very flexible and can allow user applications to directly access the Ceph storage cluster via C, C++, Java, Python, and PHP bindings. Ceph object storage also has multisite capabilities, that is, it provides solutions for disaster recovery.

The following image represents a Ceph object storage: