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Unformatted text preview: Storage Devices 5-1 Chapter 5: Storage Devices: Disks, Drives, and Media Goal The goal of this chapter is to give the reader a basic understanding of what storage is and how it differs from memory. Storage is defined and the different types of storage are briefly described. Practical comparisons among various types of storage are made to allow the reader to determine what type of storage could be used for a specific need, and to compare process and performances of alternatives. The most common interfaces are described and rated, and examples are given as exercises. Finally, a description of the functionality of storage is given together with general principles and specific tasks to maintain data and storage devices, and to avoid data loss. Types of Storage In this book, the term storage refers to nonvolatile memory that contains data for long terms without the need of power. In a microcomputer, flexible, nonvolatile storage is provided by magnetic hard disks, magnetic tape, optical disks, and several types of small cards and flash drives . In general, storage is characterized by being much slower than memory, but also more permanent and much cheaper per unit of data stored. Although it is convenient to think of types of data-holding components as neatly classified into either storage (nonvolatile) or memory (volatile), not all technologies fall clearly within one or the other. Unfortunately, there is also variation in the usage of the terms storage and memory . Although in this text we make a clear distinction between the two, keep in mind the possibility of a different usage when you read other sources. Why learn about storage? There are two main reasons: To choose the right type, size, performance, and price. To properly use and maintain data and storage devices. Consider that your computer is much like your car, or your bicycle. If you go to the bike store and indicate that you want to buy a bicycle, a good salesperson will ask what use you have in mind, what type of performance you prefer. Then, she will show you a few options and let you choose. You need to be able to understand the reason for her questions, and the relationship between performance, options, and prices, in order to make a good decision. After you buy your vehicle, you can use it and completely ignore how and why it works. Other than riding it, do nothing to maintain it. This will certainly lead to a period when Storage Devices 5-2 the operation of your car or bicycle is erratic; sometimes the car will not start right away, or it will die; the bicycle chain will get stuck; the breaks will not work. Finally, the car will not start at all, and the bike chain will fall off or snap. A very similar situation will happen with your computer, particularly with the hard disk storage. Hard disks are devices with moving parts that are known to require maintenance. They are also expected to fail completely at some point in time. I have used computers with hard disks for about twenty five years. Out of the approximately 30for about twenty five years....
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This note was uploaded on 12/28/2010 for the course PLS 21 taught by Professor Lieth during the Spring '08 term at UC Davis.
- Spring '08