Chapter 6: Heartbeat Introduction and Theory

Overview

This chapter introduces a software package called Heartbeat that gives you the ability to failover a resource from one computer to another. The following three chapters will explore Heartbeat and high-availability techniques in detail. Part III of this book will build on the techniques described here, and it will explain how to build a highly available cluster. Once you know how to use Heartbeat properly, you can deploy just about any service and make it highly available.

Note 

A highly available system has no single points of failure. A single point of failure is a single system component that upon failing causes the whole system to fail.

Heartbeat works like this: you tell Heartbeat which computer owns a particular resource (which computer is the primary server), and the other computer will automatically be the backup server. You then configure the Heartbeat daemon running on the backup server to listen to the "heartbeats" coming from the primary server. If the backup server does not hear the primary server's heartbeat, it initiates a failover and takes ownership of the resource.