File system
File system
A file system is a method and data structure that an operating system uses to control how data is stored, retrieved, and organized on a hard disk drive or other storage medium. File systems manage access to data, provide a hierarchical structure (often through directory structures), and define metadata such as file names, timestamps, permissions, and sizes. Without a file system, stored information would exist as one large block of data with no way to identify where one piece of information ends and the next begins.
The first file systems were simple flat structures used in early mainframe computers. With the rise of personal computers, more sophisticated systems like the FAT file system were developed to support floppy disks and hard drives. Later, hierarchical file systems such as NTFS (Windows), HFS+ (macOS), and ext4 (Linux) introduced journaling, extended metadata, and advanced permission models. Modern file systems also support features like snapshots, compression, encryption, and volume management.
History
Early file systems, such as the one in the IBM System/360 (1960s), used a simple catalog of files stored on punched cards or tape. The arrival of disk drives in the 1970s led to the development of the FAT file system by Microsoft for floppy disks. The Unix File System (UFS) introduced hierarchical directories, symbolic links, and inode-based metadata in the late 1970s. The 1990s saw the introduction of journaling file systems (e.g., ext3, NTFS) to reduce data loss after crashes. In the 2000s, ZFS and Btrfs brought copy-on-write, volume management, and checksumming to consumer and enterprise systems.
Features
Common features of modern file systems include:
- Hierarchical directory structure: Organizes files into directories (folders) that can contain other directories.
- File naming: Allows files to be identified by human-readable names, often with extensions indicating type.
- Metadata: Stores information such as creation date, modification date, owner, permissions, and file size.
- Permissions and security: Controls read, write, and execute access for users and groups.
- Journaling: Records changes to the file system in a log before they are applied, aiding recovery after a crash.
- Journaling: (Note: repeated for emphasis) Actually, journaling is one feature; others include symbolic links, hard links, compression, encryption, and snapshots.
Types of file systems
File systems can be classified by their design and support:
- Disk-based file systems (e.g., FAT, NTFS, ext4, HFS+)
- Flash file systems (e.g., UBIFS, F2FS) optimized for solid-state drives
- Network file systems (e.g., NFS, SMB) provide remote access
- Database file systems (e.g., BeFS) organize files using database concepts
- Virtual file systems (e.g., procfs, sysfs) expose kernel data structures as a file hierarchy
- Cryptographic file systems (e.g., TrueCrypt, eCryptfs) encrypt data on the fly