Mass Storage

One key to expanding the applications potential for information processing systems is the economic availability of online memory of extremely large capacity to permit the automatic servicing of record files. Further, mounting emphasis on "management" decision making will accelerate the emergence of true filecentered systems. This paper reviews the evolution and future trends in the implicit "mass storage." The term mass storage indicates a unit capacity ranging upward from one million characters. Such memory cannot currently be realized or projected with solid-state devices (e.g., fabricated matrices of discrete, bit elements such as core arrays). Thus, continuous (and generally interchangeable) surfaces with associated coupling transducers are exploited. The access time variability to memory locations, arising from the requisite mechanical motion, makes the structuring and organization of mass memory (software) of major significance to effective systems integration. Magnetic recording, with its unlimited surface reusability, is the firmly entrenched mass storage technology. The last decade has seen almost two orders of magnitude improvement in storage density, with in excess of 25,000 bits/sq in already used in announced products. The major technical innovation to date has been in the air-floated head which, by permitting both high density and high surface speed, brought about the introduction of mass random access memory (disk array-1956). Areas covered include systems perspectives and memory organization, memory modularity and mass storage structure, reliability and economic considerations, magnetic recording technology, and nonmagnetic media (including image storage).