High-Availability Vocabulary (Part II)

• Active-Passive Cluster - A cluster where only one node runs a given service at a time, and the other nodes are in stand-by to take over, should the need arise.
• Active-Active Cluster - A cluster where a given service is running on more then one machine at the same time.
• Fail-over - the operation of moving the service from one cluster node to another.
• I/O fencing - a mechanism used in active-passive clusters, to ensure that no matter what - at most one node will send I/O requests to a given disk.

Originally written by guy keren