Managing HP Serviceguard for Linux Ninth Edition, April 2009

Failover
Under normal conditions, a fully operating Serviceguard cluster simply monitors the
health of the cluster's components while the packages are running on individual nodes.
Any host system running in the Serviceguard cluster is called an active node. When
you create the package, you specify a primary node and one or more adoptive nodes.
When a node or its network communications fails, Serviceguard can transfer control
of the package to the next available adoptive node. This situation is shown in Figure
1-2.
Figure 1-2 Typical Cluster After Failover
After this transfer, the package typically remains on the adoptive node as long the
adoptive node continues running. If you wish, however, you can configure the package
to return to its primary node as soon as the primary node comes back online.
Alternatively, you may manually transfer control of the package back to the primary
node at the appropriate time.
Figure 1-2 does not show the power connections to the cluster, but these are important
as well. In order to remove all single points of failure from the cluster, you should
provide as many separate power circuits as needed to prevent a single point of failure
of your nodes, disks and disk mirrors. Each power circuit should be protected by an
What is Serviceguard for Linux? 25