Unix® System Management Primer Plus

Redundancy

Redundancy is the simplest technique for ensuring high availability in your systems. By duplicating components of a system, redundancy eliminates single points of failure, any of which could cause a service interruption. Many parts of a system can be made redundant, from entire servers to network interfaces. Some components that are commonly made redundant include the following:

• Servers

• Disk drives

• Network interfaces

• Communication lines (T1, T3, and so forth)

• Routers and switches

• Power supplies

• Fans

• CPUs

• Buses

Redundancy can be an expensive option. At the very least, when you purchase a redundant component, you are purchasing twice as much hardware as your service needs to function. Beyond that, you probably need other hardware, software, ...