Managing Serviceguard 11th Edition, Version A.11.16, Second Printing June 2004

Understanding Serviceguard Software Components
How the Cluster Manager Works
Chapter 370
In a cluster with four or more nodes, you may not need a cluster lock
since the chance of the cluster being split into two halves of equal size is
very small. However, be sure to configure your cluster to prevent the
failure of exactly half the nodes at one time. For example, make sure
there is no potential single point of failure such as a single LAN between
equal numbers of nodes, or that you don’t have exactly half of the nodes
on a single power circuit.