Chapter 9. Hard Disk Storage

Definition of a Hard Disk

The hard disk drive (HDD) is one of the most important and yet mysterious parts of a computer system. HDDs are sealed units used for nonvolatile data storage. Nonvolatile, or semipermanent, storage means that the storage device retains the data even when no power is supplied to the computer. Because HDDs store crucial programming and data, the consequences of failures are usually serious. To build, maintain, service, and/or upgrade a PC system properly, it is important to know how hard disks function.

HDDs contain rigid, circular platters, usually constructed of aluminum or glass (see Figure 9.1). Unlike the media inside floppy disks, the platters can’t bend or flex—hence the term hard disk ...

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