An Optimal Drum Scheduling Algorithm

Suppose a set of N records must be read or written from a drum, fixed-head disk, or similar storage unit of a computer system. The records vary in length and are arbitrarily located on the surface of the drum. The problem considered here is to find an algorithm that schedules the processing of these records with the minimal total amount of rotational latency (access time), taking into account the current position of the drum. This problem is a special case of the traveling salesman problem. The algorithm that is developed has the attractive property of exhibiting a computational complexity on the order of N log N.