Managing HP Serviceguard for Linux, Eighth Edition, March 2008

Building an HA Cluster Configuration
Configuring the Cluster
Chapter 5 179
Modifying Cluster Timing Parameters
The cmquerycl command supplies default cluster timing parameters for
HEARTBEAT_INTERVAL and NODE_TIMEOUT. Changing these parameters
will directly affect the cluster’s reformation and failover times. It is
useful to modify these parameters if the cluster is re-forming
occasionally because of heavy system load or heavy network traffic; you
can do this while the cluster is running.
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 twice HEARTBEAT_INTERVAL. A good rule
of thumb is to have at least two or three heartbeats within one
NODE_TIMEOUT.
For more information about node timeouts, see “What Happens when a
Node Times Out” on page 88 and theHEARTBEAT_INTERVAL and
NODE_TIMEOUT parameter discussions under “Cluster Configuration
Parameters” starting on page 110.