Hard Disk Storage - Upgrading and Repairing PCs - page 554

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 con-
sequences 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 . In most drives you can't remove the platters, which is why they are sometimes
called fixed disk drives.
Figure 9.1 Hard disk heads and platters.
Note
HDDs are sometimes referred to as Winchester drives . This term dates back to 1973, when
IBM introduced the model 3340 drive, which had 30MB of fixed platter and 30MB of remov-
able platter storage on separate spindles. The drive was code-named Winchester by project
leader Ken Haughton because the original capacity designation (30-30) sounded like the pop-
ular .30-30 (caliber-grains of charge) cartridge used by the Winchester 94 rifle introduced in
1895. The original 3340 “Winchester” drive was the first to use a sealed head/disk assembly,
and the name has since been applied to all subsequent drives with similar technology.