Managing Serviceguard Nineteenth Edition, Reprinted June 2011

your cluster without the need to bring it down, careful planning of the initial configuration is
required. Use the following guidelines:
• Remember the rules for cluster locks when considering expansion. A one-node cluster does
not require a cluster lock. A two-node cluster must have a cluster lock. In clusters larger than
3 nodes, a cluster lock is strongly recommended. If you have a cluster with more than 4 nodes,
you can use a Quorum Server but a cluster lock disk is not allowed.
• Networks should be pre-configured into the cluster configuration if they will be needed for
packages you will add later while the cluster is running.
• Resources monitored by EMS (Event Monitoring Service) should be pre-configured into the
cluster configuration if they will be needed for packages you will add later while the cluster
is running. Once a resource dependency is configured for any package in the cluster, it will
always be available for later packages to use. However, you cannot add a
never-before-configured resource to a package while the package is running.
Refer to the chapter on “Cluster and Package Maintenance” for more information about changing
the cluster configuration dynamically, that is, while the cluster is running.
Hardware Planning
Hardware planning requires examining the physical hardware itself. One useful procedure is to
sketch the hardware configuration in a diagram that shows adapter cards and buses, cabling,
disks and peripherals. A sample diagram for a two-node cluster is shown in Figure 35.
NOTE: Under agile addressing, the storage units in this example would have names such as
disk1, disk2, disk3, etc. See “About Device File Names (Device Special Files)” (page 77).
As of A.11.20, Serviceguard supports cluster-wide DSFs, and HP recommends that you use them.
See “About Cluster-wide Device Special Files (cDSFs)” (page 99).
Figure 35 Sample Cluster Configuration
Create a similar sketch for your own cluster. You may also find it useful to record the information
as in the sample Hardware Worksheet (page 93), indicating which device adapters occupy which
Hardware Planning 89