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Mean Time Between Failures

(MTBF, or "Mean Time Between Faults") The average time (usually expressed in hours) that a component works without failure. It is calculated by dividing the total number of failures into the total number of operating hours observed. The term can also mean the length of time a user may reasonably expect a device or system to work before an incapacitating fault occurs.

Mean Time Between Faults

Mean Time Between Failures

Mean Time To Recovery

<specification>

(MTTR) The average time that a device will take to recover from a non-terminal failure. Examples of such devices range from self-resetting fuses (where the MTTR would be very short, probably seconds), up to whole systems which have to be replaced.

The MTTR would usually be part of a maintenance contract, where the user would pay more for a system whose MTTR was 24 hours, than for one of, say, 7 days. This means the supplier is guaranteeing to have the system up and running again within 24 hours (or 7 days) of being notified of the failure.

Some devices have a MTTR of zero, which means that they have redundant components which can take over the instant the primary one fails, see RAID for example.

Nearby terms:

MDL ♦ Mean Time Between Failures ♦ Mean Time Between Faults ♦ Mean Time To Recovery

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