Mac OS X Internals: A Systems Approach

Chapter 11File Systems

A file system is an operating system component that provides an abstract view of data on a storage device. At the user-visible level, a file system’s contents are usually organized hierarchically into files and directories (or folders—we will use the terms directory and folder synonymously in this chapter and the next). A file system’s storage device is often persistent, but it is possible—and useful—to have file systems on nonpersistent devices such as physical memory.

11.1 Disks and Partitions

A common medium for storing user data is a hard^[1] disk drive. The storage space on a disk is divided at the hardware level into fundamental units called sectors. In a typical hard drive, each sector holds 512 bytes^[2] of user ...