HP Serviceguard A.11.20- Managing Serviceguard Twentieth Edition, August 2011

Figure 7 Cluster with Fibre Channel Switched Disk Array
This type of configuration uses native HP-UX or other multipathing software; see “About Multipathing”
(page 33).
Redundant Power Supplies
You can extend the availability of your hardware by providing battery backup to your nodes and
disks. HP-supported uninterruptible power supplies (UPS), such as HP PowerTrust, can provide this
protection from momentary power loss.
Disks should be attached to power circuits in such a way that mirror copies are attached to different
power sources. The boot disk should be powered from the same circuit as its corresponding node.
In particular, the cluster lock disk (used as a tie-breaker when re-forming a cluster) should have a
redundant power supply, or else it can be powered from a supply other than that used by the
nodes in the cluster. Your HP representative can provide more details about the layout of power
supplies, disks, and LAN hardware for clusters.
Many current disk arrays and other racked systems contain multiple power inputs, which should
be deployed so that the different power inputs on the device are connected to separate power
circuits. Devices with two or three power inputs generally can continue to operate normally if no
more than one of the power circuits has failed. Therefore, if all of the hardware in the cluster has
2 or 3 power inputs, then at least three separate power circuits will be required to ensure that
there is no single point of failure in the power circuit design for the cluster.
Larger Clusters
You can create clusters of up to 16 nodes with Serviceguard. Clusters of up to 16 nodes may be
built by connecting individual SPUs via Ethernet.
The possibility of configuring a cluster consisting of 16 nodes does not mean that all types of cluster
configuration behave in the same way in a 16-node configuration. For example, in the case of
shared SCSI buses, the practical limit on the number of nodes that can be attached to the same
shared bus is four, because of bus loading and limits on cable length. Even in this case, 16 nodes
Redundant Power Supplies 37