Clustering is a feature where two or more instances running on same or different machine can share same repository view. Ideally all cluster instance should have exactly same content and request to any node in cluster should return same result.

Clustering in CQ provide following benefits,

• High Availability - Cluster helps to provide high availability in case either server break down or repository break down.
• Improve Performance - Load can be balanced between cluster node to improve performance.
• Backup - Through clustering real time backup is possible if one of the node is acting as passive node.

In CQ each repository (Or instance) is referred as node. There is always one master in Cluster, Other Nodes are called as Slave. Slave and master communicate with each other over TCP/IP. If one instance comes down, other node take over as master and whole cluster continue to work.