- In Sequence (AND logic):
- Total availability = product of individual availabilities.
- Example: 2 components with 99% each → 0.99 × 0.99 = 98.01%
- One failure can bring the whole system down.
- In Parallel (OR logic):
- Total availability = 1 - (product of individual failure rates).
- Example: 2 components with 99% each → 1 - (0.01 × 0.01) = 99.99%
- System works as long as one component is up.
- Increases fault tolerance and Availability.