Managing Serviceguard 11th Edition, Version A.11.16, Second Printing June 2004

Planning and Documenting an HA Cluster
General Planning
Chapter 4 125
General Planning
A clear understanding of your high availability objectives will quickly
help you to define your hardware requirements and design your system.
Use the following questions as a guide for general planning:
1. What applications must continue to be available in the event of a
failure?
2. What system resources (processing power, networking, SPU, memory,
disk space) are needed to support these applications?
3. How will these resources be distributed among the nodes in the
cluster during normal operation?
4. How will these resources be distributed among the nodes of the
cluster in all possible combinations of failures, especially node
failures?
5. How will resources be distributed during routine maintenance of the
cluster?
6. What are the networking requirements? Are all networks and
subnets available?
7. Have you eliminated all single points of failure? For example:
• network points of failure.
• disk points of failure.
• electrical points of failure.
• application points of failure.
Serviceguard Memory Requirements
The amount of lockable memory required for Serviceguard depends on
the number of packages configured in the cluster. The following equation
provides a rough estimate of how much memory is needed:
Total Memory = 6 MB + 100 KB/package
in cluster
The total amount is needed on all nodes in the cluster, regardless of
whether a given package is on that node or not.