Which term describes the ability to continue operating in the event of a component failure?

• A. Fault tolerance
• B. Reliability
• C. Scalability
• D. QoS

Answer: (A)

Fault tolerance describes the ability of a system to continue operating even when one or more components fail. It achieves this through redundancy and automatic failover so services stay available with little or no interruption. For example, dual power supplies with automatic switchover, RAID with hot-swappable disks, or clustered servers that promote a standby node when one fails all help a system keep running despite failures. This differs from reliability, which measures how likely components are to function without failure over time, rather than how the system behaves after a failure occurs. Scalability is about handling increasing workloads by adding capacity, and QoS concerns the prioritization and guarantees of network traffic, not surviving hardware failures.