filesystem

A filesystem is a method and data structure that an operating system uses to manage files on a storage device. It defines how data is named, stored, organized, and retrieved, and it provides metadata such as permissions, timestamps, and ownership.

A filesystem sits on a physical volume from a storage device and is accessed through a mount point or device path. It uses structures like inodes or file allocation tables to track file blocks and to map names to locations.

Common types include ext4, NTFS, APFS, HFS+, XFS, and ZFS on various platforms, as well as FAT32 and exFAT for interchange. Filesystems can be optimized for stability, performance, reliability, or space efficiency.

Features may include journaling for crash resilience, snapshots and clones, encryption, compression, sparse files, and data deduplication. Some provide checksums, parity, or error-correcting capabilities to protect data integrity.

Filesystems support local storage as well as network access. Local filesystems are mounted at a directory in the operating system and may be managed by a virtual filesystem layer that abstracts different implementations.

Network filesystems such as NFS and SMB/CIFS enable remote access. Block-level or distributed filesystems, like GlusterFS or Ceph, provide scalable storage across multiple machines.

Reliability and performance are influenced by block size, caching, fragmentation, and features such as journaling or RAID integration. Regular backups and consistency checks are recommended regardless of the filesystem.

Choosing a filesystem depends on the hardware, operating system, workload, and requirements for reliability, space efficiency, and compatibility.