Chapter 9. Introduction to Linux Virtual Server

Using Red Hat Enterprise Linux, 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. By allowing multiple computers to work together in offering these critical services, system administrators can plan and execute system maintenance and upgrades without service interruption.

The chapters in this part guide you through the following steps in understanding and deploying a clustering solution based on the Red Hat Enterprise Linux Linux Virtual Server (LVS) technology:

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

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

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

9.1. Technology Overview

Red Hat Enterprise Linux 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.

• 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 specialized routing techniques to dispatch traffic to a pool of servers.

Red Hat Enterprise Linux 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

The clustering technology included in Red Hat Enterprise Linux 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 can address through service redundancy. Also, since Red Hat Enterprise Linux is designed to run on commodity hardware, it creates an environment with a high level of system availability at a fraction of the cost of fault tolerant hardware.