Managing Systems and Workgroups: A Guide for HP-UX System Administrators

Using High Availability Strategies
Using Serviceguard
Appendix A 957
Using Serviceguard
An Serviceguard cluster is a networked grouping of HP 9000 servers
(nodes) having sufficient redundancy of software and hardware that a
single point of failure will not significantly disrupt service. Applications
and services are grouped together in packages. In the event of a service,
node, or network failure, Serviceguard can automatically transfer control
of all system resources in a designated package to another node within
the cluster, allowing the applications to remain available with minimal
system interruption.
Serviceguard replaces the earlier SwitchOver product which also allowed
for redundant computer systems. Serviceguard first became available
with HP-UX 10.0.
Pros and Cons of Serviceguard
To provide a high level of availability, a typical cluster uses redundant
system components, for example, two or more SPUs and two or more
independent disks. This redundancy eliminates any single point of
failure. In general, the more redundancy, the greater access you will have
to applications, data, and supportive services in the event of failure. In
addition to hardware redundancy, the system must have the software
support that enables and controls the transfer of applications to another
SPU or network after a failure. Serviceguard provides the following
support:
• In the case of LAN failure, Serviceguard transparently switches to a
standby LAN.
• In the case of a node failure, an application is automatically
transferred from a failed processor to a functioning processor and in
a minimum amount of time.
• For software failures, an application can be restarted on the same
node or another node with minimum disruption of service.
The primary disadvantages for Serviceguard are the additional cost of
software and hardware redundancy and the added complexity of
administration. Also, hardware failures on shared components may
adversely affect all systems that are jointly connected.