5 - Large Capacity Storage Systems

Abstract

This chapter presents an introduction to the subject of large capacity storage systems. Storage system includes not only the storage medium but also the means for gaining access to specific locations in the store and for the recording and reading of information. Large capacity storage systems for digital computers may be used for either internal or external storage functions. An internal store is used to hold the program of instructions to be executed and also provides space for the storage of intermediate and final results. An external store is used for the preparation of a program and auxiliary data in a form suitable for subsequent entry into a computer. External storage media are used also for the maintenance of large files of programs and other input data as well as for the storage of output data. Whether a specific type of storage system is better suited for internal or external storage or can be used for either will depend on a number of criteria. Criteria important in the evaluation of large capacity storage systems are cost per bit, reliability, maintainability, physical size, power consumption, etc. Four important distinguishing characteristics of storage systems are operating speed, volatility, erasability, and access time.