| Cluster Service States
From the point of view of other systems in the cluster and management interfaces, nodes in the cluster may be in one of three distinct states. These states are visible to other systems in the cluster, are really the state of the Cluster Service and are managed by the Event Processor.
Offline - The system is not a fully active member of the cluster. The system and its Cluster Service may or may not be running.
Online - The system is a fully active member of the cluster. It honors cluster database updates, contributes votes to the quorum algorithm, maintains heartbeats, and can own and run Groups.
Paused - The system is a fully active member of the cluster. It honors cluster database update, contributes votes to the quorum algorithm, maintains heartbeats, but it cannot own or run Groups. The Paused state is provided to allow certain maintenance to be performed. Online and Paused are treated as equivalent states by most of the cluster software.
Node Manager
The Node Manager maintains cluster membership, and sends periodic messages, called heartbeats, to its counterparts on the other systems of the cluster to detect system failures. It is essential that all systems in the cluster always have exactly the same view of cluster membership. In the event that one system detects a communication failure with another cluster node it broadcasts a message to the entire cluster causing all members to verify their view of the current cluster membership. This is called a regroup event. Writes to potentially shared devices must be frozen until the membership has stabilized. If a Node Manager on a system does not respond, it is removed from the cluster and its active Groups must be failed over (“pulled”) to an active system. Note that the failure of a Cluster Service also causes all of its local managed resources to fail.
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