Using EMS HA Monitors

40 Chapter 2

Monitoring Disk Resources

Rules for Using the EMS Disk Monitor with MC/ServiceGuard

Rules for Using the EMS Disk Monitor

with MC/ServiceGuard

The disk monitor is designed especially for use with MC/ServiceGuard to provide

package failover if host adapters, busses, controllers, or disks fail. Here are some

examples:

• In a cluster where one copy of data is shared between all nodes in a cluster, you

may want to fail over a package if the host adapter has failed on the node

running the package. Because busses, controllers, and disks are shared, package

fail over to another node because of bus, controller, or disk failure would not

successfully run the package. To make sure you have proper failover in a shared

data environment, you must create identical package dependencies on all nodes

in the cluster. MC/ServiceGuard can then compare the resource “UP” values on

all nodes and fail 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 over

a package 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 over a package to

another node with the correct resources available. Again, the package resource

dependencies should be conﬁgured the same on all nodes.

Disk availability is based on pv_summary. See “Conﬁguring MC/ServiceGuard

Package Dependencies” in Chapter 1 for information on conﬁguring package

dependencies.

In addition to conﬁguring disks as MC/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 MC/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 you also conﬁgure requests from the SAM interface to EMS.