Managing HP Serviceguard for Linux, Seventh Edition, July 2007

Serviceguard for Linux at a Glance
What is Serviceguard for Linux?
Chapter 120
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 uninterruptible
power source. For more details, refer to the section on “Power Supply
Planning” in Chapter 4, “Planning and Documenting an HA Cluster.”