Source : Free On-Line Dictionary of Computing

Mean Time To Recovery
     
         (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.
     
        See also {Mean Time Between Failures}.
     
        (1998-05-01)