Arbitration for Data Integrity in Serviceguard Clusters
How Serviceguard Uses Arbitration
Lock Requirements
The cluster lock can be implemented either by means of a lock disk (HP-UX clusters only), a lock LUN (HP-UX and Linux clusters), or by means of a quorum server (HP-UX and Linux clusters). A one-node cluster does not require a cluster lock. A two-node cluster requires a cluster lock. In larger clusters, the cluster lock is strongly recommended. If you have a cluster with more than four nodes, a cluster lock disk or lock LUNis not allowed, but you can use a quorum server. Therefore, if the cluster is expected to grow to more than four nodes and you want to use a arbitration mechanism, you should use a quorum server. In clusters that span several data centers, a more practical alternative may be the use of arbitrator nodes. Arbitrator nodes are not a form of cluster lock, but rather they are components that prevent the cluster from ever being partitioned into two equal-sized groups of nodes.
