4.2 Fault Tolerance

What is Fault Tolerance?

Fault tolerance is the ability of a system to continue operating properly even if one or more of its components fail. Because computing systems are made of many hardware and software parts, engineers design redundancy — backup components — so a single point of failure doesn't crash the whole system.

Redundancy in the Internet

The Internet is a great example of a fault-tolerant system. It uses multiple, redundant paths between devices so data can be rerouted automatically if a router, cable, or server fails. Packets can take different routes to reach the same destination, keeping the network reliable and resilient to failure of individual routers or connections.

Redundancy Beyond Networks

Fault tolerance also applies to storage and systems: backup servers, multiple copies of data on different machines, and redundant power supplies all help prevent data loss or downtime. Distributing data and processing across many machines reduces the risk that a single hardware failure causes a total system failure.

Key terms

Fault tolerance

The ability of a system to continue operating properly even if one or more components fail.

Redundancy

Duplicate components or data included in a system so it can keep functioning if one part fails.

Single point of failure

A component that, if it fails, causes the entire system to fail because there is no backup.

Rerouting (Internet)

The process of sending data packets along alternate paths when a router or connection fails.

Redundant data storage

Keeping multiple copies of data on different servers/machines to prevent loss if one fails.

Try an AP-style question

What makes a network fault-tolerant?

1. Redundant paths between devices
2. Very fast computers
3. A single path between devices
4. Encrypted packets only