Advances in Data Storage Technology

3484 Words Nov 17th, 2010 14 Pages
Advances in Data Storage Technology

Contents
I. Introduction 3
II. Purpose of storage 4
III. Hierarchy of storage 6 A. Primary storage 6 B. Secondary storage 7 C. Tertiary storage 7 D. Off-line storage 8
IV. Characteristics of storage 9 A. Volatility 9 B. Mutability 9 C. Accessibility 10 D. Addressability 10 E. Capacity 11 F. Performance 11 G. Energy use 11
V. Fundamental storage technologies 12 A. Semiconductor 12 B. Magnetic 12 C. Optical 13 D. Paper 14 E. Uncommon 14
VI. Related technologies 17 A. Network
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Generally, the lower a storage is in the hierarchy, the lesser its bandwidth and the greater its access latency is from the CPU. This traditional division of storage to primary, secondary, tertiary and off-line storage is also guided by cost per bit.

III. Hierarchy of storage

A. Primary storage:

Primary storage (or main memory or internal memory), often referred to simply as memory, is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required. Any data actively operated on is also stored there in uniform manner. Historically, early computers used delay lines, Williams’s tubes, or rotating magnetic drums as primary storage. By 1954, those unreliable methods were mostly replaced by magnetic core memory. Core memory remained dominant until the 1970s, when advances in integrated circuit technology allowed semiconductor memory to become economically competitive. This led to modern random-access memory (RAM). It is small-sized, light, but quite expensive at the same time. (The particular types of RAM used for primary storage are also volatile, i.e. they lose the information when not powered). As the RAM types used for primary storage are volatile (cleared at start up), a computer containing only such storage would not have a source to read instructions from, in order to start the computer. Hence, non-volatile primary storage containing a small startup
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