Cluster Suite Components

Cluster Infrastructure

• provides fundamental functions for nodes to work together as a cluster: configuration-file management, membership management, lock management and fencing

CMAN

• keeps track of cluster quorum by monitoring the count of cluster nodes

• If more than half the cluster nodes are active, the cluster has quorum. if half of the nodes (or fewer) are active, the cluster does not have quorum and all cluster activity is stopped. cluster quorum prevents the occurrence of a “split-brain” condition.

• “split-brain” - a condition where two instances of the same cluster are running, a split-brain condition would allow each cluster instance to access cluster resources without knowledge of the other cluster instance, resulting in corrupted cluster integrity.

CLVM

• provides volume management of cluster storage

RGMANAGER

• manages and provides failover capabilities for collections of resources called services, resource groups, or resource trees in a cluster

• allows admins to define, configure and monitor cluster services.

• in the event of a node failure, rgmanager will relocate the clustered service to another node with minimal service disruption.

Stopping services

• service rgmanager stop

• service clvmd stop

• service cman stop

Starting services

• service cman start

• service clvmd start

• service rgmanager start