Managing Serviceguard Eighteenth Edition, September 2010

NOTE: If you are using CVM or CFS, you cannot change MEMBER_TIMEOUT or
AUTO_START_TIMEOUT while the cluster is running. This is because they affect the
aggregate failover time, which is only reported to the CVM stack on cluster startup.
You also cannot change the quorum configuration while SG-CFS-pkg is running.
Previewing the Effect of Cluster Changes
Many variables affect package placement, including the availability of cluster nodes;
the availability of networks and other resources on those nodes; failover and failback
policies; and package weights, dependencies, and priorities, if you have configured
them. You can preview the effect on packages of certain actions or events before they
actually occur.
For example, you might want to check to see if the packages are placed as you expect
when the cluster first comes up; or preview what happens to the packages running on
a given node if the node halts, or if the node is then restarted; or you might want to
see the effect on other packages if a currently disabled package has package switching
enabled, or if a package halts and cannot restart because none of the nodes on its
node_list is available.
Serviceguard provides two ways to do this: you can use the preview mode of
Serviceguard commands, or you can use the cmeval (1m) command to simulate
different cluster states.
Alternatively, you might want to model changes to the cluster as a whole; cmeval
allows you to do this; see “Using cmeval” (page 362).
What You Can Preview
You can preview any of the following, or all of them simultaneously:
• Cluster bring-up (cmruncl)
• Cluster node state changes (cmrunnode, cmhaltnode)
• Package state changes (cmrunpkg, cmhaltpkg)
• Package movement from one node to another
• Package switching changes (cmmodpkg -e)
• Availability of package subnets, EMS resources, and storage
• Changes in package priority, node order, dependency, failover and failback policy,
node capacity and package weight
Using Preview mode for Commands and in Serviceguard Manager
The following commands support the -t option, which allows you to run the command
in preview mode:
• cmhaltnode [–t] [–f] <node_name>
• cmrunnode [–t] <node_name>
Reconfiguring a Cluster 361