Placement optimization program: a practical solution to the disk file assignment problem

We describe a practical mathematical formulation and solution of the so-called 'File Assignment Problem' (FAP) for computer disks. Our FAP solution has been implemented in a PL/I program known as the Placement Optimization Program (POP). The algorithm consists of three major components -- two heuristic optimization models and a queueing network model. POP has been used in validation studies to assign files to disks in two IBM MVS complexes. The resulting savings in I/O response times were 22% and 25%, respectively. Throughout the paper we shall emphasize the real-world nature of our approach to the disk FAP, which we believe sets it apart from previous attempts.