Using High Availability Monitors (June 2007)

Monitoring Disk Resources
Rules for Using the HA Disk Monitor with ServiceGuard
Chapter 2 37
Rules for Using the HA Disk Monitor with
ServiceGuard
The HA Disk Monitor is designed for use with ServiceGuard to trigger
package failover if host adapters, buses, controllers, or disks fail. Here
are some examples:
• In a cluster where one copy of data is shared between all nodes in the
cluster, you may want to fail a package if the host adapter has failed
on the node running the package. Because buses, controllers, and
disks are shared, package failover will not run the package
successfully. ServiceGuard can then compare the resource UP values
on all nodes and fail the package over to the node that has the correct
resources available.
• In a cluster where each node has its own copy of data, you may want
to fail a package over to another node for any number of reasons:
— Host adapter, bus, controller, or disk failure
— Unprotected data (the number of copies is reduced to one)
— Performance has degraded because one of the PV links has failed
For example, in a cluster of Web servers where each node has a copy
of the data and users are distributed for load balancing, you can fail
a package over to another node with the correct resources available.
Disk availability is based on pv_summary. See the manual Using the
Event Monitoring Service (HP Part Number B7612-90015) for
information on configuring package dependencies.
In addition to configuring disks as ServiceGuard package dependencies,
you may also want to have alerts sent to a system management tool such
as HP OpenView IT/Operations or Network Node Manager. Although
ServiceGuard and EMS work together to provide package failover, they
do not send events or log the source of the failure. Also, failures may not
cause a package to fail over, but may expose a single point of failure that
you want to know about. Therefore, it is recommended that you also
configure requests from the HP SMH interface to EMS.