HP XC System Software Installation Guide Version 4.0

1.9.1 What Is Improved Availability?
A service availability infrastructure is built into the HP XC System Software, which enables an
availability tool to fail over a subset of services to nodes that have been designated as a second
server of the service. Improved availability protects against service failure if a node that is serving
vital services becomes unresponsive or becomes unavailable.
You have the flexibility to decide which availability tool you want to use to manage and migrate
specified services to a second server if the first server is not available. You can install one or more
availability tools to manage the services that have been configured for improved availability.
The availability tool is responsible for starting, stopping, and monitoring those services; you do
not use HP XC commands for those tasks.
HP Serviceguard product is the recommended availability tool, but you can install and configure
other third party tools of your choice. If you install an availability tool other than HP Serviceguard,
the third-party vendor or the product documentation is responsible for providing customer
support for the tool.
How Does Availability Work?
Using the procedures described in this document, you use the cluster_config utility to assign
a service or services to be served from two nodes through a mechanism called an availability set.
An availability set associates two individual nodes so that one node acts as the first server and
the other node acts as the second server of the service.
The cluster_config utility associates the service with an IP address alias (for example,
172.20.64.200). Client nodes are configured to connect to the service by communicating with the
IP alias.
The availability tool is responsible for configuring the IP alias and for starting the service on the
primary server. The tool is also responsible for detecting if a node becomes unresponsive or
unavailable. If that happens, the availability tool uses the IP alias to start the service on the second
server in the availability set. Client nodes do not detect that the first server has gone down.
1.9.2 How to Configure Improved Availability
Table 1-1 provides a summary of how to set up and configure improved availability of services.
Detailed information or procedures are provided at the appropriate points in the system
installation and configuration process, as noted in the second column of the table.
Table 1-1 Improved Availability Summary
Appropriate Task Details
Are Provided HereTask
Section 1.9.3 (page 28)1. Decide which availability tool or tools you want to use; this tool manages the services
for which improved availability has been configured. Then, obtain or purchase, install,
and configure the availability tool or tools.
Section 1.9.4 (page 28)2. Write translator and supporting scripts for the availability tool if you are not using HP
Serviceguard.
Then, position the translator and related scripts in the
/opt/hptc/availability/availability_tool directory.
Section 1.9.5 (page 29)
3. Decide how you want to make the hptc_cluster file system highly available.
Section 1.9.6 (page 29)4. Decide which nodes you want to configure into availability sets.
Section 1.9.7 (page 30)5. Determine the services for which you want to configure improved availability.
1.9 Planning a Service Availability Strategy 27