Managing HP Serviceguard for Linux, Sixth Edition, August 2006

Building an HA Cluster Configuration
Configuring the Cluster
Chapter 5 169
Modifying Cluster Timing Parameters
The cmquerycl command supplies default cluster timing parameters for
HEARTBEAT_INTERVAL and NODE_TIMEOUT. Changing these parameters
will directly impact the cluster’s reformation and failover times. It is
useful to modify these parameters if the cluster is reforming occasionally
due to heavy system load or heavy network traffic.
The default value of 2 seconds for NODE_TIMEOUT leads to a best case
failover time of 30 seconds. If NODE_TIMEOUT is changed to 10 seconds,
which means that the cluster manager waits 5 times longer to timeout a
node, the failover time is increased by 5, to approximately 150 seconds.
NODE_TIMEOUT must be at least 2*HEARTBEAT_INTERVAL. A good rule of
thumb is to have at least two or three heartbeats within one
NODE_TIMEOUT.
Adding or Removing Nodes While the Cluster is
Running
You can reconfigure the cluster by adding or removing nodes while the
cluster is up and running. The procedures are described in the chapter on
“Cluster and Package Maintenance.”