Chapter 1: Clustering Concepts and General Overview

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In order to understand IBM's clustering solution, we should have a clear understanding of clusters, Linux, and the Open Source movement. This chapter introduces basic clustering concepts and terminology. The knowledge gained throughout this chapter will serve as an effective foundation for the rest of this redbook. This redbook has not been developed to teach individuals how to design clustered solutions, because the IBMCluster 1350 provides a solution to this dilemma for us all. Rather, it is intended to allow the reader to become more familiar with the components of a cluster and the roles that they play. This redbook will provide the fundamental knowledge you will need in order to configure the Cluster 1350 for your environment, it will also be a valuable aid in developing a plan for its installation.

1.1 What is a cluster

In its simplest form, a cluster is two or more computers that work together to provide a solution. This should not be confused with a more common client-server model of computing, where an application may be logically divided such that one or more clients request services of one or more servers. The idea behind clusters is to join the computing powers of the nodes involved to provide higher scalability, more combined computing power, or to build in redundancy to provide higher availability. So, rather than a simple client making requests of one or more servers, clusters utilize multiple machines to provide a more powerful computing environment through a single system image.

Clusters of computers must be somewhat self-aware, that is, the work being done on a specific node often must be coordinated with the work being done on other nodes. This can result in complex connectivity configurations and sophisticated inter-process communications between the nodes of a cluster. In addition, the sharing of data between the nodes of a cluster through a common file system is almost always a requirement. There are many other complexities that are introduced by clusters, such as the operational considerations of dealing with a potentially large number of computers as a single resource.

For additional information, refer to the following Web site:

http://www.pc.ibm.com/ww/eserver/xseries/clustering/info.html

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