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 a device has redundant power supplies, connect each power supply to a separate power circuit. 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 each device in a cluster has three power supplies, you will need a minimum of three separate power circuits to eliminate electrical power as a single point of failure for the cluster.

In the case of hardware with only one power supply, no more than half the nodes should share a single power circuit. If a power source supplies exactly half the nodes, it must not also supply the cluster disk lock or quorum server, or the cluster will not be able to re-form 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 disk (if any). If you use a quorum server, or quorum server cluster, make sure each quorum server node has a power source 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 (or VxVM disk 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. You can use the Power Supply Worksheet to record 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:

Be sure to follow UPS and cabinet power limits as well as SPU power limits.

Power Supply Configuration Worksheet

The following worksheet will help you organize and record your specific power supply configuration. This worksheet is an example; blank worksheets are in Appendix F “Blank Planning Worksheets”. Make as many copies as you need.

========================================================================== SPU Power:     Host Name ____ftsys9__________ Power Supply _____1_______________     Host Name ____ftsys10_________ Power Supply _____2_______________ ========================================================================== Disk Power: Disk Unit __________1_______________ Power Supply ____3________________ Disk Unit __________2_______________ Power Supply ____4________________ Disk Unit __________________________ Power Supply _____________________ Disk Unit __________________________ Power Supply _____________________ Disk Unit __________________________ Power Supply _____________________ Disk Unit __________________________ Power Supply _____________________ ========================================================================== Tape Backup Power: Tape Unit __________________________ Power Supply _____________________ Tape Unit __________________________ Power Supply _____________________ ========================================================================== Other Power: Unit Name __________________________ Power Supply _____________________ Unit Name __________________________ Power Supply _____________________