HARD DISK DRIVE TECHNOLOGY A few years ago, a query about the health of a person's hard disk drive would have been met with a blank stare. Nowadays, almost everyone is aware of this remarkable electronic storage medium that is part of every modern computer, even though most users remain ignorant of the complexity of hard drive technology. In the early days of computing, an information record of a computer' s memory content was kept on punched cards similar to the way in which an automated piano stores the keynote sequences on a piano roll. Later, magnetic tape was used to store electronic signals and is still the favoured means of economically backing up the contents of hard drives. However, accessing information sequentially stored on tape is slow since the electronic data must be input through a fixed head in a single pass. Hard disk drives solve this problem by incorporating a spinning platter on which magnetic data can be made accessible via a moving head that re...