Managing Serviceguard Eighteenth Edition, September 2010

IMPORTANT: When multiple heartbeats are configured, heartbeats are sent in parallel;
Serviceguard must receive at least one heartbeat to establish the health of a node. HP
recommends that you configure all subnets that connect cluster nodes as heartbeat
networks; this increases protection against multiple faults at no additional cost.
Heartbeat IP addresses are usually on the same subnet on each node, but it is possible
to configure a cluster that spans subnets; see “Cross-Subnet Configurations” (page 41).
For more information about heartbeat requirements, see the entry for HEARTBEAT_IP,
under “Cluster Configuration Parameters ” starting on (page 143). For timeout
requirements and recommendations, see the MEMBER_TIMEOUT parameter description
in the same section. For troubleshooting information, see “Cluster Re-formations Caused
by MEMBER_TIMEOUT Being Set too Low” (page 415). See also “Cluster Daemon:
cmcld” (page 55).
Manual Startup of Entire Cluster
A manual startup forms a cluster out of all the nodes in the cluster configuration.
Manual startup is normally done the first time you bring up the cluster, after
cluster-wide maintenance or upgrade, or after reconfiguration.
Before startup, the same binary cluster configuration file must exist on all nodes in the
cluster. The system administrator starts the cluster in Serviceguard Manager or with
the cmruncl command issued from one node. The cmruncl command can only be
used when the cluster is not running, that is, when none of the nodes is running the
cmcld daemon.
During startup, the cluster manager software checks to see if all nodes specified in the
startup command are valid members of the cluster, are up and running, are attempting
to form a cluster, and can communicate with each other. If they can, then the cluster
manager forms the cluster.
Automatic Cluster Startup
An automatic cluster startup occurs any time a node reboots and joins the cluster. This
can follow the reboot of an individual node, or it may be when all nodes in a cluster
have failed, as when there has been an extended power failure and all SPUs went down.
Automatic cluster startup will take place if the flag AUTOSTART_CMCLD is set to 1
in /etc/rc.config.d/cmcluster. When any node reboots with this parameter set
to 1, it will rejoin an existing cluster, or if none exists it will attempt to form a new
cluster.
Dynamic Cluster Re-formation
A dynamic re-formation is a temporary change in cluster membership that takes place
as nodes join or leave a running cluster. Re-formation differs from reconfiguration,
How the Cluster Manager Works 61