Managing HP Serviceguard for Linux, Eighth Edition, March 2008

Building an HA Cluster Configuration
Managing the Running Cluster
Chapter 5 195
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 wish to include a list of all cluster nodes in this message,
together with additional cluster-specific information.
The /etc/motd file may be customized to include cluster-related
information.
Managing a Single-Node Cluster
The number of nodes you will need for your HP Serviceguard cluster
depends on the processing requirements of the applications you want to
protect.
In a single-node cluster, a quorum server is not required, since there is
no other node in the cluster. The output from the cmquerycl command
omits the quorum server 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 LANs that you want
Serviceguard to monitor. For LANs that already have IP addresses,
specify them with the STATIONARY_IP parameter, rather than the
HEARTBEAT_IP parameter.
Single-Node Operation
Single-node operation occurs in a single-node cluster or in a multi-node
cluster, following a situation where all but one node has failed, or where
you have shut down all but one node, which will probably have
applications running. As long as the HP Serviceguard daemon cmcld is
active, other nodes can re-join the cluster at a later time.
If the HP Serviceguard daemon fails when in single-node operation, it
will leave the single node up and your applications running. This is
different from the loss of the HP Serviceguard daemon in a multi-node
cluster, which halts the node with a reboot, and causes packages to be
switched to adoptive nodes. It is not necessary to halt the single node in
this scenario, since the application is still running, and no other node is