Quorum Conditions: General Rule

A valid quorum ensures correct replication and fault tolerance. As a general rule, a group of candidate services must satisfy all three of the following conditions to form a valid quorum.

(For special exceptions, see Quorum Behaviors.)

• Majority:  The number of candidate services that satisfy these conditions must be strictly greater than half of the number of services in the cluster definition (that is, a simple majority).
• Reachable:  A majority of the defined services must be running and able to communicate with one another.
• Non-Empty:  A majority of the defined services must be non-empty. (A service is empty when it starts or restarts without loading saved state. A service that has successfully joined a quorum is no longer empty.)