# Fault Tolerance vs High Availability

> Chapter 56 of the Courseiva AZ-900 curriculum — https://courseiva.com/learn/az-900/fault-tolerance-concepts

**Official objective:** 1.5 — Cloud Concepts

## Introduction

This chapter covers fault tolerance vs availability concepts. AZ-900 tests under 1.5.

## Handling Failures Gracefully

A bridge is designed to stay upright even with traffic loss (fault tolerance) vs. a bridge that fails immediately if one cable breaks (no tolerance). Fault tolerance is the design philosophy.

## Core explanation

Fault tolerance is the ability to handle component failures without total failure. It's related to availability but distinct: availability is the percentage of time working; fault tolerance is the ability to survive failures.

## Real-world context

A system with fault tolerance continues working even if individual servers fail, automatically restarting failed ones.

## Exam focus

Objective 1.5 expects understanding that fault tolerance and availability are related but distinct.

## Step by step

1. **Design for failures** — Assume components will fail; design around it.
2. **Add redundancy** — Multiple instances so one failure doesn't stop the system.
3. **Monitor and heal** — Detect failures and automatically restart failed instances.

## Key takeaways

- Fault tolerance handles failures without total failure.
- Related to but distinct from availability.
- Achieved through redundancy and monitoring.

## FAQ

**What is fault tolerance?**

The ability of a system to handle component failures without experiencing a total system failure, achieved through redundancy and automatic recovery.

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Interactive version with quiz and diagrams: https://courseiva.com/learn/az-900/fault-tolerance-concepts