Introduction to Hard Disk Drives

The last chapter introduced the general concept of an I/O device and showed you how the OS might interact with such a beast. In this chapter, we dive into more detail about one device in particular: the hard disk drive. These drives have been the main form of persistent data storage in computer systems for decades and much of the development of file system technology (coming soon) is predicated on their behavior. Thus, it is worth understanding the details of a disk’s operation before building the file system software that manages it. Many of these details are available in excellent papers by Ruemmler and Wilkes“An Introduction to Disk Drive Modeling” by C. Ruemmler, J. Wilkes. IEEE Computer, 27:3, March 1994. A terrific introduction to the basics of disk operation. Some pieces are out of date, but most of the basics remain. and Anderson, Dykes, and Riedel“More Than an Interface: SCSI vs. ATA” by Dave Anderson, Jim Dykes, Erik Riedel. FAST ’03, 2003. One of the best recent-ish references on how modern disk drives really work; a must read for anyone interested in knowing more..

CRUX: HOW TO STORE AND ACCESS DATA ON DISK How do modern hard-disk drives store data? What is the interface? How is the data actually laid out and accessed? How does disk scheduling improve performance?