The storage hierarchy is a natural structure, given the set of available technologies and their price and performance characteristics. The physical structure of the storage subsystem is described, and the flow of data through the system is traced. The concept of a storage hierarchy is discussed, and the specific components of the IBM storage hierarchy from the processor highspeed buffer (HSB) to the on-line DASD configuration are described in detail. Trade-offs between technologies and the interactions among the levels of the hierarchy are discussed. In particular, the importance of the I/O boundary, processor storage volatility, and data sharing are highlighted. A continuous increase in virtual storage capacity can be seen in the evolution of large-scale operating systems, and MVS/ESA™ now provides the ultimate virtual capacity and function. New virtual structures available in MVS/ESA are discussed, and their relationship to the storage hierarchy is studied. The importance of storage to the performance and cost of a large processing system leads to a discussion of guidelines for storage configuration and data placement within the hierarchy. 95193. Mr. Brady joined IBM in 1961 as a systems engineer-scientific. He has held various positions in the Data Processing, Advanced Systems Development, Systems Products, Data Systems, and General Products Divisions. He was manager ofDSD systems technology and strategy, where he initiated the development of the Enterprise Systems Architecture and expanded storage. Mr. Brady is currently product manager ofGPD storage systems strategy and architecture, where he is responsible for performance analysis, architecture, and the development of new product opportunities. Mr. Brady graduated from Creighton University in 1961, with a B.S. degree in mathematics. He has done graduate work in mathematics and business administration and is a graduate of the
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