Managing HP Serviceguard for Linux, Tenth Edition, September 2012

If you enter a value greater than 60 seconds
(60,000,000 microseconds), cmcheckconf and
cmapplyconf will note the fact, as confirmation
that you intend to use a large value.
Minimum supported values:
• 3 seconds for a cluster with more than one
heartbeat subnet.
• 14 seconds for a cluster that has only one
heartbeat LAN
With the lowest supported value of 3 seconds, a
failover time of 4 to 5 seconds can be achieved.
NOTE: The failover estimates provided here
apply to the Serviceguard component of failover;
that is, the package is expected to be up and
running on the adoptive node in this time, but the
application that the package runs may take more
time to start.
Keep the following guidelines in mind when
deciding how to set the value.
Guidelines: You need to decide whether it's more
important for your installation to have fewer (but
slower) cluster re-formations, or faster (but possibly
more frequent) re-formations:
• To ensure the fastest cluster re-formations, use
the minimum value applicable to your cluster.
But keep in mind that this setting will lead to
a cluster re-formation, and to the node being
removed from the cluster and rebooted, if a
system hang or network load spike prevents
the node from sending a heartbeat signal
within the MEMBER_TIMEOUT value. More
than one node could be affected if, for
example, a network event such as a
broadcast storm caused kernel interrupts to
be turned off on some or all nodes while the
packets are being processed, preventing the
nodes from sending and processing heartbeat
messages.
Cluster Configuration Planning 115