In this release,
an availability infrastructure has been introduced to improve availability
of some services currently associated with the head node as well as
NAT, LVS, and Nagios. The availability infrastructure allows you the
flexibility to select and use the availability tool you prefer to
manage the services.
In this release, HP Serviceguard is the recommended
availability tool, and it must be purchased and licensed separately
from HP.
In general, availability tools monitor nodes,
services and resources, and restart the services and resources on
another node, as necessary. In most cases, IP aliases are used for
the failover of services so that client nodes can continue to communicate
with an IP address. The client nodes do not detect that the actual
node has changed.
HP has supplied translator and other essential
scripts for HP Serviceguard for you. The translator and scripts obtain
the availability information in the configuration and management database
and create the appropriate HP Serviceguard configuration files. When
you install the Serviceguard RPM from the HP XC DVD, the HP
Serviceguard scripts are loaded into the /opt/hptc/availability/serviceguard directory. This RPM enables Serviceguard to operate on an HP XC system.
Any availability tool you decide to use must be
installed on the head node before invoking the cluster_config utility.
Defining an availability solution requires advance
planning. You must determine in advance the services for which you
want to enable improved availability and which nodes will be assigned
with those services. Then, you must ensure that you assign the appropriate
roles to the nodes defined in the availability set.
New Commands Associated with Improved Availability. The following commands have been added to the HP XC command
suite to support improved availability:
transfer_to_avail turns over service management responsibilities to the appropriate
availability tool or tools
transfer_from_avail returns service management responsibilities to HP XC commands
rather than the availability tool or tools
New Functionality Provided by the /sbin/service Script. When improved availability is configured, the
behavior of the /sbin/service script differs as
follows: a filter script handles services that are being managed by
the availability tool differently than standard services. Services
with improved availability are stopped, started, restarted and provide
status through the availability tool, not through the standard service
script mechanisms. All other /sbin/service commands
are processed by the standard service script.
How to plan a service availability strategy and
configure availability sets is documented in the HP XC System Software Installation Guide.
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