Periodically, each instance in the cluster “checks in” with the quorum device, creating a quorum device heartbeat that enables instances to monitor the status of the cluster. Instances use the device heartbeat to:
Determine if the quorum device is accessible. If an instance fails to write the heartbeat to the quorum device, the instance may have has lost its storage area network (SAN) link, or it may be blocked from the cluster devices.
Read the heartbeat values from the quorum disk while it is starting. If the instance detects no changes in the heartbeat after a configured period of time, the instance determines the cluster is not running.
Instances do not use the quorum heartbeat to detect instance failure.
