Introduction and considerations

Both Sun Cluster and VERITAS Cluster use agents to greatly simplify cluster configuration. Each type of resource supported in a cluster is associated with an agent. An agent is an installed program designed to control a particular resource type. For Sun Cluster or VERITAS Cluster to bring an Oracle resource online, it does not need to understand Oracle; it simply passes the online command to the Oracle agent. The Oracle agent knows to call the server manager and issue the appropriate command. Both Sun Cluster and VERITAS cluster have Oracle, DB2, Informix®, and SyBase agents. Many other enterprise agents are also available. Some of these agents come with the base cluster software, and some require an additional purchase. Sun Cluster can also use the VERITAS Volume Manager.

Sun Cluster supports up to eight nodes while VERITAS supports up to 32 nodes. Sun Cluster is integrated with OPS and OPFS, but VERITAS Cluster does not support OPS and OPFS.

The Sun Cluster, or SunPlex system, is an integrated hardware and software solution that is used to create highly available and scalable services. The SunPlex system extends the Solaris operating environment into a cluster operating system. The commonly used versions are Sun Cluster 2.2 and Sun Cluster 3.0. There are some differences between the versions. For example, Sun Cluster 2.2 requires a terminal concentrator for failure fencing, but later products do not depend on the terminal concentrator.

The Sun Cluster we configured for WebSphere is shown in Figure 12-7. It can: Reduce or eliminate system downtime because of software or hardware failures. Ensure availability of data and applications to end users, regardless of the kind of failure that would normally take down a single-server system. Increase application throughput by enabling services to scale to additional processors by adding nodes to the cluster. Provide enhanced availability of the system by enabling you to perform maintenance without shutting down the entire cluster.

Sun Cluster configurations, as shown in Figure 12-7, tolerate the following types of single-point failures:

Server operating environment failure because of a crash or a panic

Data service failure

Server hardware failure

Network interface failure

Disk media failure

Figure 12-7 Sun Cluster configuration for WebSphere

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