Linux Enterprise Cluster: Build a Highly Available Cluster with Commodity Hardware and Free Software

I'll start with the terminology used to describe high availability. I'm not going to split hairs at this point—I'll do that later, when I explore each concept in depth. The important thing here is that I introduce a vocabulary that allows us to talk about multiple computers working together to accomplish a task.

When a program runs, it is called a process. A process running on a Linux system is called a daemon. A daemon and the effects it produces is called a service. A service is called a resource when it is combined with its operating environment (configuration files, data, network mechanism used to access it, and so forth). A failover occurs when a resource moves from one computer to another. A proper failover or high-availability configuration has no single point of failure.^[1]

^[1]I'm departing from the Red Hat cluster terminology here, but I am using these terms as they are defined by Linux-ha advocates (see http://www.linux-ha.org).