HP Serviceguard manual Changing the System Message, Managing a Single-Node Cluster

There are three cases:

•The cluster is not running on any node, all cluster nodes must be reachable, and all must be attempting to start up. In this case, the node attempts to form a cluster consisting of all configured nodes.

•The cluster is already running on at least one node. In this case, the node attempts to join that cluster.

•Neither is true: the cluster is not running on any node, and not all the nodes are reachable and trying to start. In this case, the node will attempt to start for the AUTO_START_TIMEOUT period. If neither of the other two cases becomes true in that time, startup will fail.

To enable automatic cluster start, set the flag AUTOSTART_CMCLD to 1 in /etc/rc.config.d/ cmclusteron each node in the cluster; the nodes will then join the cluster at boot time.

Here is an example of the /etc/rc.config.d/cmcluster file:

#************************ CMCLUSTER ************************

#Highly Available Cluster configuration

#@(#) $Revision: 72.2 $

#
# AUTOSTART_CMCLD:	If set to 1, the node will attempt to
#	join it's CM cluster automatically when
#	the system boots.
#	If set to 0, the node will not attempt
#	to join it's CM cluster.
#
AUTOSTART_CMCLD=1

NOTE: The /sbin/init.d/cmcluster file may call files that Serviceguard stores in /etc/ cmcluster/rc. This directory is for Serviceguard use only! Do not move, delete, modify, or add files in this directory.

Changing the System Message

You may find it useful to modify the system's login message to include a statement such as the following:

This system is a node in a high availability cluster. Halting this system may cause applications and services to start up on another node in the cluster.

You might want to include a list of all cluster nodes in this message, together with additional cluster-specific information.

The /etc/issue and /etc/motd files may be customized to include cluster-related information.

Managing a Single-Node Cluster

The number of nodes you will need for your Serviceguard cluster depends on the processing requirements of the applications you want to protect. You may want to configure a single-node cluster to take advantage of Serviceguard’s network failure protection.

In a single-node cluster, a cluster lock is not required, since there is no other node in the cluster. The output from the cmquerycl command omits the cluster lock information area if there is only one node.

You still need to have redundant networks, but you do not need to specify any heartbeat LANs, since there is no other node to send heartbeats to. In the cluster configuration file, specify all the LANs that you want Serviceguard to monitor. Use the STATIONARY_IP parameter, rather than HEARTBEAT_IP, to specify LANs that already have IP addresses. For standby LANs, all that is required is the NETWORK_INTERFACE parameter with the LAN device name.

224 Building an HA Cluster Configuration