The quorum disk is required for a 2-node cluster and recommended for a 4-node cluster. The quorum disk is used in the cluster as a voting disk and only when the majority of votes are present will the processing of I/O occur. Each member has a node vote, and during startup, rules are applied to allow the member to join the cluster. The voting rules include a quorum disk if defined. All members in a cluster must agree on the same number of expected votes.

Nodes are considered voting or nonvoting members. A node has either one or zero votes. A member with a vote of one is considered a voting member, and a member with zero votes is a nonvoting member.

Voting members are allowed to form a cluster. Nonvoting members are allowed to join an existing cluster but not to form a cluster.

Quorum votes are calculated using the following formula:

   Quorum Votes = round down((cluster_expected_votes + 2) /2)

The value for cluster_expected_votes can be found using the clu_get_info command. For example a node in the cluster expects three votes to operate.

    # clu_get_info -full  grep -i expected        Cluster expected votes = 3

In a 2-node cluster configured with one vote per node and the expected number of votes set to two, the loss of either node will cause the cluster to lose quorum and all applications...