Disks in digital video
7.1 Types of disk
Disk drives came into being as random-access file-storage devices for digital computers. The explosion in the growth of personal computers has fuelled demand for low-cost high-density disk drives and the rapid access offered is increasingly finding applications in digital video. After lengthy development, optical disks are also emerging in digital video applications.
Figure 7.1 shows that, in a disk drive, the data are recorded on a circular track. In hard-disk drives, the disk rotates at several thousand rev/min so that the head-to-disk speed is of the order of 100 miles per hour. At this speed no contact can be tolerated, and the head flies on a boundary layer of air turning with the disk at ...