An administrator investigating an incident is concerned about the downtime of a critical server due...

Mean Time To Repair (MTTR) is a key metric used to estimate the average time required to repair a failed component or system and restore it to operational status. In this case, the administrator would rely on MTTR to estimate how long it will take to fix the critical server’s failed drive and get it back online.

Mean Time Between Failures (MTBF) measures the expected operational lifespan between failures, so it does not provide an estimate of repair time.

Recovery Time Objective (RTO) refers to the maximum allowable downtime for a system or service before unacceptable impact occurs, which is a planning metric rather than an actual repair time measure.

Recovery Point Objective (RPO) defines the maximum acceptable data loss measured in time and relates to backup frequency rather than repair duration.

Therefore, MTTR is the appropriate metric to estimate the time to fix a failed drive. This concept is detailed in the Resilience and Physical Security chapter within the Security Operations domain of the SY0-701 exam【6:Chapter 9†CompTIA Security+ Study Guide】