HFS Plus

Journaling file system developed by Apple / From Wikipedia, the free encyclopedia

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HFS Plus or HFS+ (also known as Mac OS Extended or HFS Extended) is a journaling file system developed by Apple Inc. It replaced the Hierarchical File System (HFS) as the primary file system of Apple computers with the 1998 release of Mac OS 8.1. HFS+ continued as the primary Mac OS X file system until it was itself replaced with the Apple File System (APFS), released with macOS High Sierra in 2017. HFS+ is also one of the formats supported by the iPod digital music player.

Quick facts: Developer(s), Full name, Introduced, Partitio...
Developer(s)Apple Inc.
Full nameHierarchical File System Plus
IntroducedJanuary 19, 1998; 25 years ago (1998-01-19) with Mac OS 8.1
Partition identifierApple_HFS (Apple Partition Map)
0xAF (MBR) HFS and HFS+
Apple_HFSX (Apple Partition Map) when HFSX
Directory contentsB-tree
File allocationBitmap
Bad blocksB-tree
Max. volume size8 exabyte[1]
Max. file size8 EB[2]
Max. number of files4,294,967,295 (232 − 1)
Max. filename length255 characters (255 UTF-16 encoding units, normalized to Apple-modified variant of Unicode Normalization Format D)
Allowed characters in filenamesUnicode, any character, including NUL. OS APIs may limit some characters for legacy reasons
Dates recordedaccess, attributes modified, backed up, contents modified, created
Date rangeJanuary 1, 1904 – February 6, 2040[3]
Date resolution1 s
AttributesColor (3 bits, all other flags 1 bit), locked, custom icon, bundle, invisible, alias, system, stationery, inited, no INIT resources, shared, desktop
File system permissionsUnix permissions, NFSv4 ACLs (Mac OS X v10.4 onward)
Transparent compressionPartial (decmpfs, on Mac OS X 10.6 and higher)[4]
Transparent encryptionYes (on Mac OS X 10.7 and up). Per-home directory encryption is available with AES[clarification needed] using HFS+-formatted .dmg volumes on OS X versions prior to 10.7 but later than Mac OS X 10.3
Supported operating systemsMac OS 8.1, Mac OS 9, macOS/iOS/tvOS/watchOS/Darwin, Linux, Microsoft Windows (through Boot Camp IFS drivers)

Compared to its predecessor HFS, also called Mac OS Standard or HFS Standard, HFS Plus supports much larger files (block addresses are 32-bit length instead of 16-bit) and using Unicode (instead of Mac OS Roman or any of several other character sets) for naming items. Like HFS, HFS Plus uses B-trees to store most volume metadata, but unlike most file systems that support hard links, HFS Plus supports hard links to directories. HFS Plus permits filenames up to 255 characters in length, and n-forked files similar to NTFS, though until 2005 almost no system software took advantage of forks other than the data fork and resource fork. HFS Plus also uses a full 32-bit allocation mapping table rather than HFS's 16 bits, improving the use of space on large disks.