HP XC System Software Administration Guide Version 3.1

2 Improved Availability
The improved availability feature of the HP XC system offers the following benefits:
• It enables services and, thus, user jobs, to continue to run, even after a node failure.
• It enables you to run new jobs.
The improved availability feature relies on an availability tool controlling nodes and services in an
availability set. The HP XC System Software provides commands to transfer control of services to the
availability tool.
This chapter addresses the following topics:
• “Purpose of the Availability Tool” (page 43)
• “Services Eligible for Improved Availability” (page 43)
• “Availability Sets” (page 44)
• “HP Serviceguard Tasks” (page 44)
• “Transferring Control of Services” (page 47)
2.1 Purpose of the Availability Tool
With the improved availability feature, the HP XC System Software transfers management of specific
services and nodes to an availability tool. During the cluster_config operation, you define a set of
nodes and services as an availability set. The availability tool manages the configured services and the
nodes, and relocates the service to another configured node in the event of a node failure.
The availability tool is not bundled with the HP XC System Software; you must order it from the
manufacturer and install it according to the manufacturer's prescribed installation procedure. The HP XC
System Software Installation Guide provides information on the installation needs of the availability tool.
One such availability tool is HP Serviceguard, which is shown in examples in this chapter. If you prefer
to use another availability tool, for example, the open source Heartbeat tool, you can create scripts in a
tools-specific directory to run the necessary commands. For more information, contact the HP XC support
team at:
[e-mail]
The software for the availability tools is located in a directory that the manufacturer chooses. The HP XC
System Software provides a directory, /opt/hptc/availability/, under which tool-specific directories
are created. These subdirectories contain scripts and routines that automate the configuration and
management of the availability tool on the HP XC system.
During the system startup, which is discussed in Chapter 3 (page 49), you issue a command that transfers
the control of specific services previously assigned to a node in an availability set to the availability tool.
This tool manages those services, aliases, and the failover from one node to another.
The availability tool monitors the node health, services, and aliases. If, for example, a node fails, the
availability tool restarts the services that node was responsible for on another node in its availability set.
Before reconfiguring the HP XC system, you must issue another command to remove its aliases and to
return control of the services from the availability tool to the HP XC system.
2.2 Services Eligible for Improved Availability
The following services are eligible for Improved availability:
• dbserver for the Command and Management Database
• lvs for the Linux Virtual Server
• nat for Network Address Translation
• nagios for the Nagios Master service
NOTE: The nagios_monitor service is not eligible.
For more information on services, see Chapter 4 (page 55).
2.1 Purpose of the Availability Tool 43