Chapter 1. Overview

A block is a sequence of bytes, for example, a 512-byte block of data. Block-based storage interfaces are the most common way to store data with rotating media such as:

The ubiquity of block device interfaces makes a virtual block device an ideal candidate to interact with a mass data storage system like Red Hat Ceph Storage.

Ceph Block Devices, also known as Reliable Autonomic Distributed Object Store (RADOS) Block Devices (RBDs), are thin-provisioned, resizable and store data striped over multiple Object Storage Devices (OSD) in a Ceph Storage Cluster. Ceph Block Devices leverage RADOS capabilities such as:

Ceph Block Devices interact with OSDs by using the librbd library.

Ceph Block Devices deliver high performance with infinite scalability to Kernel Virtual Machines (KVMs) such as Quick Emulator (QEMU), and cloud-based computing systems like OpenStack and CloudStack that rely on the libvirt and QEMU utilities to integrate with Ceph Block Devices. You can use the same cluster to operate the Ceph Object Gateway and Ceph Block Devices simultaneously.