Managing Serviceguard 12th Edition, March 2006

Planning and Documenting an HA Cluster
Power Supply Planning
Chapter 4144
Power Supply Planning
There are two sources of power for your cluster which you will have to
consider in your design: line power and uninterruptible power sources
(UPS). Loss of a power circuit should not bring down the cluster.
Frequently, servers, mass storage devices, and other hardware have two
or three separate power supplies, so they can survive the loss of power to
one or more power supplies or power circuits. If your cluster has devices
with redundant power supplies, connect the each devices power supplies
to separate power circuits. This way the failure of a single power circuit
will not cause the complete failure of any critical device in the cluster.
For example, if all devices in a cluster have three power supplies, it will
require a minimum of three separate power circuits to eliminate the
power as a single point of failure for the cluster.
For services with only one power supply, no more than half of the nodes
should be on a single power source. If a power source supplies exactly
half of the nodes, it must not also supply the cluster disk lock or quorum
server, or the cluster will not be able to reform after a failure. See the
section on cluster locks in “Cluster Configuration Planning” for more
information.
To provide a high degree of availability in the event of power failure, use
a separate UPS at least for each node's SPU and for the cluster lock. Be
sure that quorum server nodes have separate power sources from every
cluster they serve. Be sure that quorum server or the cluster lock disks
that will be configured as members of separate physical volume groups
are connected to different power supplies. This last rule enables disk
mirroring to take place between physical disks that are connected to
different power supplies as well as being on different I/O buses.
To prevent confusion, it is suggested that you label each hardware unit
and power supply unit clearly with a different unit number. Indicate on
the Power Supply Worksheet the specific hardware units you are using
and the power supply to which they will be connected. Enter the
following label information on the worksheet:
Host Name
Enter the host name for each SPU.
Disk Unit
Enter the disk drive unit number for each disk.
Tape Unit
Enter the tape unit number for each backup device.