Managing Serviceguard Fifteenth Edition, reprinted May 2008

Understanding Serviceguard Software Components
How the Cluster Manager Works
Chapter 3 67
Each node sends its heartbeat message at a rate specified by the cluster
heartbeat interval. The cluster heartbeat interval is set in the cluster
configuration file, which you create as a part of cluster configuration,
described fully in Chapter 5, “Building an HA Cluster Configuration,” on
page 197.
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 the /etc/rc.config.d/cmcluster file. 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, which is a permanent modification of the
configuration files. Re-formation of the cluster occurs under the following
conditions (not a complete list):