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Mean time to repair (MTTR) is a basic measure of the maintainability of repairable items. It represents the average time required to repair a failed component or device. [ 1 ] Expressed mathematically, it is the total corrective maintenance time for failures divided by the total number of corrective maintenance actions for failures during a ...
Mean Time To Recover (MTTR) is the length of time required to restore operation to specification. This includes three values. Mean Time To Discover; Mean Time To Isolate; Mean Time To Repair; Mean Time To Discover is the length of time that transpires between when a failure occurs and the system users become aware of the failure.
It includes logistics time, ready time, and waiting or administrative downtime, and both preventive and corrective maintenance downtime. This value is equal to the mean time between failure divided by the mean time between failure plus the mean downtime (MDT). This measure extends the definition of availability to elements controlled by the ...
Mean time to recovery (MTTR) [1] [2] [3] is the average time that a device will take to recover from any failure. Examples of such devices range from self-resetting fuses (where the MTTR would be very short, probably seconds), to whole systems which have to be repaired or replaced.
where MTTR is the mean time to repair. The MTTF of a system is the sum of MTTF S and MTTF D. To understand the relationship between MTTF S and MTTF D consider the case of a switch that turns a motor on or off. The switch has two failure modes: the switch can fail stuck closed or the switch can fail stuck open.
Time magazine used the term in their June 16, 1942, issue: "Last week U.S. citizens knew that gasoline rationing and rubber requisitioning were snafu." [5] Most reference works, including the Random House Webster's Unabridged Dictionary, supply an origin date of 1940–1944, generally attributing it to the United States Army. [citation needed]
A concept which is closely related to MTBF, and is important in the computations involving MTBF, is the mean down time (MDT). MDT can be defined as mean time which the system is down after the failure. Usually, MDT is considered different from MTTR (Mean Time To Repair); in particular, MDT usually includes organizational and logistical factors ...
In such systems the mean time between failures should be long enough for the operators to have sufficient time to fix the broken devices (mean time to repair) before the backup also fails. It is helpful if the time between failures is as long as possible, but this is not specifically required in a fault-tolerant system.