Managing HP Serviceguard for Linux, Tenth Edition, September 2012

separate from that of every cluster it serves. If you use software mirroring, make sure
power supplies are not shared among different physical volume groups; this allows you
to set up mirroring between physical disks that are not only on different I/O buses, but
also connected to different power supplies.
To prevent confusion, 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.
Other Unit Enter the number of any other unit.
Power Supply Enter the power supply unit number of the UPS to which the host or
other device is connected.
Be sure to follow UPS, power circuit, and cabinet power limits as well as SPU power
limits.
Power Supply Configuration Worksheet
The Power Supply Planning worksheet (page 324) will help you organize and record your
specific power supply configuration. Make as many copies as you need.
Cluster Lock Planning
The purpose of the cluster lock is to ensure that only one new cluster is formed in the
event that exactly half of the previously clustered nodes try to form a new cluster. It is
critical that only one new cluster is formed and that it alone has access to the disks
specified in its packages. You can specify a lock LUN or a quorum server as the cluster
lock. For more information about the cluster lock, see“Cluster Lock” (page 40).
NOTE: You cannot use more than one type of lock in the same cluster.
Cluster Lock Requirements
A one-node cluster does not require a lock. Two-node clusters require the use of a cluster
lock, and a lock is recommended for larger clusters as well. Clusters larger than four
nodes can use only a quorum server as the cluster lock.
For information on configuring lock LUNs and the Quorum Server, see “Setting up a Lock
LUN” (page 166), “Specifying a Lock LUN” (page 182), and the HP Serviceguard Quorum
Server Version A.04.00 Release Notes at http://www.docs.hp.com -> High
Availability -> Quorum Server.
96 Planning and Documenting an HA Cluster