MarketExtent (file systems)
Company Profile

Extent (file systems)

In computing, an extent is a contiguous area of storage reserved for a file in a file system, represented as a range of block numbers, or tracks on count key data devices. A file can consist of zero or more extents; one file fragment requires one extent. The direct benefit is in storing each range compactly as two numbers, instead of canonically storing every block number in the range. Also, extent allocation results in less file fragmentation.

Adoption
The systems supporting file system extents include the following: • APFS Apple File System • ASM Automatic Storage Management Oracle's database-oriented file system • BFS BeOS, Zeta and Haiku operating systems • Btrfs Extent-based copy-on-write (COW) file system for Linux • EFS Extent File System SGI's first-generation file system for IRIXext4 Linux file system (when the configuration enables extents the default in Linux since version 2.6.23) • Files-11 OpenVMS file system • HFS and HFS Plus Hierarchical File System Apple Macintosh file systems • High Performance File System (HPFS) on OS/2, eComStation and ArcaOS • IceFS IceFileSystem optional file system for MorphOSJFS Journaled File System used by AIX, OS/2/eComStation/ArcaOS and Linux operating systems • ISO 9660 Extent-based file system for optical disc media • MPE File System the file system of the Multi-Programming Executive operating system. • NTFS used by Windows • OCFS2 Oracle Cluster File System a shared-disk file system for Linux • Reiser4 Linux file system (in "extents" mode) • SINTRAN III file system used by early computer company Norsk DataUDF Universal Disk Format standard for optical media • VERITAS File System enabled via the pre-allocation API and CLI • XFS SGI's second-generation file system for IRIX and Linux Adoption outside of file systems include the following: • Microsoft SQL Server versions support 64 KB extents consisting of eight 8 KB pages. • Oracle Database groups blocks into extents and extents into segments. == See also ==
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