Using EMS HA Monitors

26 Chapter 1

Installing and Using EMS

Conﬁguring MC/ServiceGuard Package

Dependencies

This section describes how to use SAM to create package dependencies on EMS

resources. This creates an EMS request to monitor that resource and to notify

MC/ServiceGuard when that resource reaches a critical user-deﬁned level.

MC/ServiceGuard will then failover the package. Here are some examples of how

EMS might be used:

• 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

In this sort of 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.

This information for creating requests is also valid for EMS monitors sold with

other products (ATM or OTS, for example) and for user-written monitors written

according to developer speciﬁcations in Writing Monitors for the Event Monitoring

Service (EMS).

NOTE You should create the same requests on all nodes in an MC/ServiceGuard cluster.

A package can depend on any resource monitored by an EMS monitor. To create

package dependencies, choose create or modify a package from the Package

Conﬁguration interface under the High Availability Clusters subarea of SAM,

Figure 1-7. You see a new option called “Specify Package Resource Dependencies.”