HDD

To many people, a hard disk is a "black box" of sorts--it is thought of as just a small device that "somehow" stores data. There is nothing wrong with this approach of course, as long as all you care about is that it stores data. If you use your hard disk as more than just a place to "keep stuff", then you want to know more about your hard disk. It is hard to really understand the factors that affect performance, reliability and interfacing without knowing how the drive works internally. Fortunately, most hard disks are basically the same on the inside. While the technology evolves, many of the basics are unchanged from the first PC hard disks in the early 1980s.

Photograph of a modern SCSI hard disk, with major components annotated. The logic board is underneath the unit and not visible from this angle.

Original image © Western Digital Corporation Image used with permission.

In this section we dive into the guts of the hard disk and discover what makes it tick. We look at the various key components, discuss how the hard disk is put together, and explore the various important technologies and how they work together to let you read and write data to the hard disk. My goal is to go beyond the basics, and help you really understand the design decisions and tradeoffs made by hard disk engineers, and the ways that new technologies are being employed to increase capacity and improve performance.