The High Availability Add-On is a clustered system that provides reliability, scalability, and availability to critical production services. The High Availability Add-On consists of a number of major components. Cluster infrastructure provides fundamental functions for nodes to work together as a cluster: configuration-file management, membership management, lock management, and fencing. High availability Service Management provides failover of services from one cluster node to another in case a node becomes inoperative. Cluster administration tools serve for setting up, configuring, and managing the High Availability Add-On.