Filesystems abstract the physical view of storage devices from users, and virtualize storage area on a disk for each valid user of the system through abstract containers called files and directories. Files serve as containers for user data and directories act as containers to a group of user files. In simple words, operating systems virtualize a view of a storage device for each user as a set of directories and files. Filesystem services implement routines to create, organize, store, and retrieve files, and these operations are invoked by user applications through appropriate system call interfaces.

We will begin this discussion by looking at the layout of a simple filesystem, designed to manage a standard magnetic storage disk. This discussion will help us comprehend key terms and concepts related to disk management in general. A typical filesystem implementation however involves appropriate data structures which describe the organization of file data on disk, and operations which enable applications to execute file I/O.