Managing Serviceguard Eighteenth Edition, September 2010

• electrical points of failure.
• application points of failure.
Serviceguard Memory Requirements
Serviceguard requires approximately 15.5 MB of lockable memory.
Planning for Expansion
When you first set up the cluster, you indicate a set of nodes and define a group of
packages for the initial configuration. At a later time, you may wish to add additional
nodes and packages, or you may wish to use additional disk hardware for shared data
storage. If you intend to expand 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 4-1.
122 Planning and Documenting an HA Cluster