Red Hat CLUSTER SUITE - CONFIGURING AND MANAGING A CLUSTER 2006 Manual page 47

Chapter 2. Hardware Installation and Operating System Configuration 31
It is not recommended to use a single UPS infrastructure as the sole source of power for the
cluster. A UPS solution dedicated to the cluster is more flexible in terms of manageability
and availability.
A complete UPS system must be able to provide adequate voltage and current for a pro-
longed period of time. While there is no single UPS to fit every power requirement, a
solution can be tailored to fit a particular configuration.
If the cluster disk storage subsystem has two power supplies with separate power cords, set
up two UPS systems, and connect one power switch (or one node's power cord if not using
power switches) and one of the storage subsystem's power cords to each UPS system. A
redundant UPS system configuration is shown in Figure 2-2.
Figure 2-2. Redundant UPS System Configuration
An alternative redundant power configuration is to connect the power switches (or the
nodes' power cords) and the disk storage subsystem to the same UPS system. This is
the most cost-effective configuration, and provides some protection against power failure.
However, if a power outage occurs, the single UPS system becomes a possible single point
of failure. In addition, one UPS system may not be able to provide enough power to all
the attached devices for an adequate amount of time. A single UPS system configuration is
shown in Figure 2-3.