MC/ServiceGuard Background

Figure 19-1 shows a basic ServiceGuard setup in which two systems both connect to vg01 and vg02. There are package definitions on the respective systems for the applications they are running in the top of the diagram. The bottom of Figure 19-1 shows that package2 is started on systemA when there is a failure on systemB. This is a cluster reformation when a failure occurs. This diagram depicts the fundamental operation of ServiceGuard; that is, an application on a failed system is started on a backup system.

The application package contains all of the information related to applications in the ServiceGuard environment. For each package there is a package control file and package control script. The package configuration file contains all dependencies for the application such as the package name, service name, subnet, and so on. The package control script is run to start or stop the application package. These are ASCII files.

In addition to the ASCII files used to define the package and start and stop it, there is a cluster configuration file. This file has in it parameters such as the cluster name, maximum number of configured packages, and so on. This file, along with the package configuration file, are combined to produce a binary file that is distributed to all of the nodes. The cmapplyconf command is used to produce the binary file.

Figure 19-2 shows the relationship between some of the components and files in a ServiceGuard environment.

This diagram is by no means complete, but it shows the relationship between some of the more important components in a ServiceGuard environment. The next section covers creating a simple ServiceGuard cluster including the steps required and the files related to the cluster.