Quorum Configurations

Quorum configurations depend on the number of nodes in the cluster:

• Two-Node Clusters - Two quorum votes are required for a two-node cluster to form. These two votes can come from the two cluster nodes, or from just one node and a quorum device. Nevertheless, a quorum device must be configured in a two-node cluster to ensure that a single node can continue if the other node fails.

• More Than Two-Node Clusters - You should specify a quorum device between every pair of nodes that shares access to a disk storage enclosure. For example, suppose you have a three-node cluster similar to the one shown in Figure 3-3. In this figure, nodeA and nodeB share access to the same disk enclosure and nodeB and nodeC share access to another disk enclosure. There would be a total of five quorum votes, three from the nodes and two from the quorum devices shared between the nodes. A cluster needs a majority of the quorum votes to form.

  Specifying a quorum device between every pair of nodes that shares access to a disk storage enclosure is not required or enforced by Sun Cluster software. However, it can provide needed quorum votes for the case where an N+1 configuration degenerates into a two-node cluster and then the node with access to both disk enclosures also fails. If you configured quorum devices between all pairs, the remaining node could still operate as a cluster.

  See Figure 3-3 for examples of these configurations.

Figure 3-3 Quorum Device Configuration Examples