What is the difference between high availability and fault tolerance?

Question

Accepted Answer

**High Availability** — minimal downtime. **Fault Tolerance** — continues on failure.

**High Availability:**
- Minimize downtime.
- Redundancy.
- Automatic failover.
- 99.99% uptime.

```
High Availability:
[Primary] → [Replica]
  If Primary fails → Replica takes over
  (Minimal downtime)
```

**Fault Tolerance:**
- Continue on failure.
- No downtime.
- Redundant components.
- Zero downtime.

```
Fault Tolerance:
[Node 1] [Node 2] [Node 3]
  If Node 1 fails → Others continue
  (No interruption)
```

**Key differences:**
- **HA** — minimal downtime.
- **Fault Tolerance** — zero downtime.
- **HA** — quick recovery.
- **Fault Tolerance** — no interruption.

Systems Analyst: What is the difference between high availability and fault tolerance?