Arbitration For Data Integrity in Serviceguard Clusters, July 2007

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.