Hit ratio of caching disk buffers

Hit ratio is the primary measure of disk cache buffer efficiency, and may be contrasted against cache overhead. A technique to calculate the lower bound of hit ratio based on cache overhead is presented. A method to calculate average hit ratio based on I/O tracing is also developed. Finally, an example is cited showing that a hit ratio as low as 14% will offer a performance improvement over similar disk drives equipped with noncaching buffers.<>