Managing Serviceguard 13th Edition, February 2007

Building an HA Cluster Configuration
Preparing Your Systems
Chapter 5 197
Plan the cluster’s roles and validate them as soon as possible. If your
organization’s security policies allow it, you may find it easiest to create
group logins. For example, you could create a MONITOR role for user
operator1 from ANY_CLUSTER_NODE. Then you could give this login
name and password to everyone who will need to monitor your clusters.
Defining Name Resolution Services
When you employ any user-level Serviceguard command (including
cmviewcl), the command uses name lookup to obtain the addresses of all
the cluster nodes. If name services (such as DNS) are not available, the
command could hang or return an unexpected networking error message.
NOTE If such a hang or error occurs, Serviceguard and all protected
applications will continue working even though the command you issued
does not. That is, only the Serviceguard configuration commands (and
corresponding Serviceguard Manager functions) are affected, not the
cluster daemon or package services.
To avoid this problem, configure all cluster nodes to use the /etc/hosts
file in addition to DNS or NIS. This also allows Serviceguard to continue
functioning fully following a primary LAN failure. See “Safeguarding
against Loss of Name Resolution Services” on page 197 for more
information.
NOTE HP also recommends that you make DNS highly available, either by
using multiple DNS servers or by configuring DNS into a Serviceguard
package.
Safeguarding against Loss of Name Resolution Services
This section explains how to create a robust name-resolution
configuration that will allow cluster nodes to continue communicating
with one another if DNS or NIS services fail. If a standby LAN is
configured, this approach also allows the cluster to continue to function
fully (including commands such as cmrunnode and cmruncl) after the
primary LAN has failed.