MTTR is a metric used to measure which of the following attributes?

MTTR, or Mean Time to Repair, is a key metric specifically used to assess the reliability of a system or component. Reliability refers to the ability of a system to perform its intended functions under specified conditions for a designated period of time. MTTR provides insights into how quickly a system can recover from failures by measuring the average time taken to repair a system or restore it to operational state after a failure occurs.

A lower MTTR indicates that a system can be repaired more quickly, which correlates to higher reliability because it means that downtime—the duration when systems are non-operational due to repairs—is minimized. In contrast, the other attributes, such as functionality, portability, and efficiency, do not directly connect to the concept of repair times or recovery from failures, which is why MTTR is specifically relevant to reliability metrics.