Chapter 5. Introduction

Using Red Hat Enterprise Linux AS 2.1, it is possible to create highly available server clustering solutions able to withstand many common hardware and software failures with little or no interruption of critical services. In addition, Red Hat Enterprise Linux AS, by allowing multiple computers to work together in offering these critical services, can help system administrators plan and execute system maintenance and upgrades without any service interruption.

This manual guides you through the following steps in understanding and deploying a clustering solution based on Red Hat Enterprise Linux AS's Linux Virtual Server (LVS) technology:

• Explains the Linux Virtual Server technology used by Red Hat Enterprise Linux AS to create a load-balancing cluster.

• Explains how to configure a Red Hat Enterprise Linux AS LVS cluster.

• Walks you through the Piranha Configuration Tool, a graphical interface used for configuring and monitoring an LVS cluster.

An accompanying manual, the Red Hat Cluster Manager Installation and Administration Guide, explains how to deploy a clustering solution based on Red Hat Cluster Manager:

• Learn about the Red Hat Cluster Manager's high-availability services technology.

• Explain how to set up the appropriate hardware and software to use Red Hat Cluster Manager.

Technology Overview

Red Hat Enterprise Linux AS implements highly available server solutions via clustering. It is important to note that cluster computing consists of three distinct branches:

• Compute clustering (such as Beowulf) uses multiple machines to provide greater computing power for computationally intensive tasks. This type of clustering is not addressed by Red Hat Enterprise Linux AS.

• High-availability (HA) clustering uses multiple machines to add an extra level of reliability for a service or group of services.

• Load-balance clustering uses a router to dispatch traffic to a pool of servers.

Red Hat Enterprise Linux AS addresses the latter two types of clustering technology. Using a collection of programs to monitor the health of the systems and services in the cluster.

Note

Red Hat Enterprise Linux AS's clustering technology is not synonymous with fault tolerance. Fault tolerant systems use highly specialized and often very expensive hardware to implement a fully redundant environment in which services can run uninterrupted by hardware failures. However, fault tolerant systems do not account for operator and software errors which Red Hat Enterprise Linux AS can address through service redundancy. Also, since Red Hat Enterprise Linux AS is designed to run on readily available hardware, it creates an environment with a high level of system availability at a fraction of the cost of fault tolerant hardware.