Source : Free On-Line Dictionary of Computing

Reliability, Availability, Serviceability
     
         (RAS) Three key
        attributes of a computing system design.  See {reliability},
        {availability}, and {serviceability}.
     
        The term "RAS" is fairly common in the computing industry
        (particularly computers and storage) as computing becomes more
        fundamental.  For example, a vehicle may depend on dozens of
        computers, and the consequences of the failure can be
        significant (e.g., an ambulance's engine won't start).
     
        (2000-08-13)