The true delight is in the finding out rather than in the knowing. — Isaac Asimov

I found this document which contains also a lot of useful informations and basics about clustering even if you not plan to use the RedHat suite.

Cluster Basics

A cluster is two or more computers (called nodes or members) that work together to perform a task. There are four major types of clusters:

1. Storage clusters

provide a consistent file system image across servers in a cluster, allowing the servers to simultaneously read and write to a single shared file system. A storage cluster simplifies storage administration by limiting the installation and patching of applications to one file system. Also, with a cluster-wide file system, a storage cluster eliminates the need for redundant copies of application data and simplifies backup and disaster recovery.

2. High availability clusters

provide highly available services by eliminating single points of failure and by failing over services from one cluster node to another in case a node becomes inoperative. Typically, services in a high-availability cluster read and write data (via read-write mounted file systems). Therefore, a high-availability cluster must maintain data integrity as one cluster node takes over control of a service from another cluster node. Node failures in a high-availability cluster are not visible from clients outside the cluster. (High-availability clusters are sometimes referred to as failover clusters.)

3. Load balancing clusters

dispatch network service requests to multiple cluster nodes to balance the request load among the cluster nodes. Load balancing provides cost-effective scalability because you can match the number of nodes according to load requirements. If a node in a load-balancing cluster becomes inoperative, the load-balancing software detects the failure and redirects requests to other cluster nodes. Node failures in a load-balancing cluster are not visible from clients outside the cluster.

4. High performance clusters

use cluster nodes to perform concurrent calculations. A high-performance cluster allows applications to work in parallel, therefore enhancing the performance of the applications. (High performance clusters are also referred to as computational clusters or grid computing.)

via Cluster Suite Overview.