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 3–2. 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 3–2 for examples of these configurations.

Figure 3–2 Quorum Device Configuration Examples