Managing Serviceguard Eighteenth Edition, September 2010

• Deploying applications in this environment requires careful consideration; see
“Implications for Application Deployment” (page 202).
• If a monitored_subnet (page 296) is configured for PARTIAL monitored_subnet_access
in a package’s configuration file, it must be configured on at least one of the nodes
on the node_name list for that package.
Conversely, if all of the subnets that are being monitored for this package are
configured for PARTIAL access, each node on the node_name list must have at least
one of these subnets configured.
— As in other cluster configurations, a package will not start on a node unless the
subnets configured on that node, and specified in the package configuration
file as monitored subnets, are up.
Implications for Application Deployment
Because the relocatable IP address will change when a package fails over to a node on
another subnet, you need to make sure of the following:
• The hostname used by the package is correctly remapped to the new relocatable
IP address.
• The application that the package runs must be configured so that the clients can
reconnect to the package’s new relocatable IP address.
In the worst case (when the server where the application was running is down),
the client may continue to retry the old IP address until TCP’s tcp_timeout is reached
(typically about ten minutes), at which point it will detect the failure and reset the
connection.
For more information, see the white paper Technical Considerations for Creating a
Serviceguard Cluster that Spans Multiple IP Subnets, at www.hp.com/go/
hpux-serviceguard-docs.
Configuring a Package to Fail Over across Subnets: Example
To configure a package to fail over across subnets, you need to make some additional
edits to the package configuration file.
NOTE: This section provides an example for a modular package; for legacy packages,
see “Configuring Cross-Subnet Failover” (page 383).
Suppose that you want to configure a package, pkg1, so that it can fail over among all
the nodes in a cluster comprising NodeA, NodeB, NodeC, and NodeD.
NodeA and NodeB use subnet 15.244.65.0, which is not used by NodeC and NodeD;
and NodeC and NodeD use subnet 15.244.56.0, which is not used by NodeA and
NodeB. (See “Obtaining Cross-Subnet Information” (page 248) for sample cmquerycl
output).
202 Planning and Documenting an HA Cluster