Filsystem

A filesystem is the software layer that arranges how data is stored on a storage device and how it is retrieved. It provides a namespace of files and directories, and stores metadata such as permissions, ownership, timestamps, and access control. Data is allocated on the medium in units such as blocks, with a mapping from files to blocks managed by structures like inodes or file allocation tables. Files may be referenced by hard links or symbolic links.

Implementations run as part of an operating system and may be local (on a hard disk or SSD) or remote (networked or distributed). A filesystem is mounted to a path in the directory tree to become accessible. Features vary by design and include journaling for crash recovery, snapshots, encryption, compression, and data integrity checks. They also define limitations on file sizes, volume sizes, and directory counts.

Common examples include ext4, XFS, Btrfs, and ZFS on Unix-like systems; NTFS on Windows; APFS on Apple platforms; and FAT32 or exFAT for broad compatibility. File systems differ in performance, reliability, scalability, and cross-platform support, and choosing one affects durability, speed, and interoperability.

Historically, file systems evolved from simple layouts with flat name spaces to sophisticated systems with hierarchical namespaces, metadata integrity, and features such as journaling and snapshots. The term encompasses both local and networked storage and remains central to data management in modern computing.