Sun Cluster Concepts Guide for Solaris OS

Recommended Quorum Configurations

This section shows examples of quorum configurations that are recommended. For examples of quorum configurations you should avoid, see Bad Quorum Configurations.

Quorum in Two–Host Configurations

Two quorum votes are required for a two-host cluster to form. These two votes can derive from the two cluster hosts, or from just one host and a quorum device.

Figure 3–2 Two–Host Configuration

Illustration: Shows Host A and Host B with one quorum
device that is connected to two hosts.

Quorum in Greater Than Two–Host Configurations

Quorum devices are not required when a cluster includes more than two hosts, as the cluster survives failures of a single host without a quorum device. However, under these conditions, you cannot start the cluster without a majority of hosts in the cluster.

You can add a quorum device to a cluster that includes more than two hosts. A partition can survive as a cluster when that partition has a majority of quorum votes, including the votes of the hosts and the quorum devices. Consequently, when adding a quorum device, consider the possible host and quorum device failures when choosing whether and where to configure quorum devices.

Illustration: Config1: HostA-D. A/B connect to (->) QD1.
C/D -> QD2. Config2: HostA-C. A/C -> QD1. B/C -> QD2. Config3: HostA-C ->
one QD.