Review of current proposed technologies for mass storage systems

Several years ago, let us say 1965, there were few serious technological challengers for large main memories and file storage systems for computers. Magnetic cores and rotating magnetic disks were the undisputed champions. While there was no lack of alternatives in the mid 1960´s, cores and disks still offered potential improvements which could not easily be challenged by other technologies. The status of computing systems has advanced to a point where currently, as in the past, larger and faster access storage is needed. While there still exists room for improvement in cores and disk technology, the tradeoffs between size, speed, and cost suggest that other technologies may now offer certain advantages. As a result, numerous technologies have appeared recently to offer alternatives for large storage systems. Some of the more notable proposed technologies currently receiving considerable attention in the published literature will be reviewed. After a discussion of the limitations and technical aspects of magnetic recording and a systems analysis of direct access storage, a review of the more advanced technologies of surface wave acoustics, magnetooptic beam addressed memories, magnetic bubbles, switchable resistances, and integrated circuit memories of various types is undertaken. A discussion of the device concept with a possible system implementation for mass storage is presented along with conceivable densities, speed, advantages and disadvantages, and inherent limitations. The essential conclusion is that when all the necessary requirements for a storage system are taken into consideration, none of the more advanced technologies have a clear-cut distinct appeal over any other. Each has its own special advantages and attraction but only at the expense of some other features, such as special operating environments (e.g., low temperature), special operating modes (e.g., shift register), a limited range of applicability, or limited potential for further improvements in performance. There remains room for other inventions, particularly for storage systems with access times considerably faster than mechanical devices (i.e., one millisecond) but slower and cheaper than commonplace electronic speeds (i.e., one microsecond). However, because of the stringent requ- irements imposed by storage systems and cost/performance tradeoffs, it does not appear likely that these will be forthcoming in the near future.