^ IBM introduced JFS with the initial release of AIX Version 3.1 in 1990. This file system now called JFS1. The new JFS, on which the Linux port was based, was first shipped in OS/2 Warp Server for e-Business in 1999. The same sourcebase was also used for release JFS2 on AIX 5L.

^ any support for FAT32 up to Windows NT4; Windows 2000 was the first NT-based Windows OS that received the ability to work with it. Microsoft first introduced FAT32 in MS-DOS 7.1 Windows 95 OSR2 (OEM Service Release 2) and then later in Windows 98 . NT-based Windows did not havesupport for FAT32 up to Windows NT4; Windows 2000 was the first NT-based Windows OS that received the ability to work with it.

a b c d e For filesystems that have variable allocation unit (block/cluster) sizes, a range of size are given, indicating the maximum volume sizes for the minimum and the maximum possible allocation unit sizes of the filesystem (e.g. 512 bytes and 128 KiB for FAT — which is the cluster size range allowed by the on-disk data structures, although some Installable File System drivers and operating systems do not support cluster sizes larger than 32 KiB ).

a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak In these filesystems the directory entries named "." and ".." have special status. Directory entries with these names are not prohibited, and indeed exist as normal directory entries in the on-disk data structures. However, they are mandatory directory entries, with mandatory values, that are automatically created in each directory when it is created; and directories without them are considered corrupt.

^ The file size in the inode is 1 8-bit byte followed by 1 16-bit word, for 24 bits. The actual maximum was 8,847,360 bytes, with 7 singly-indirect blocks and 1 doubly-indirect block; PWB/UNIX 1.0's variant had 8 singly-indirect blocks, making the maximum 524,288 bytes or half a MiB

^ The actual maximum was 1,082,201,088 bytes, with 10 direct blocks, 1 singly-indirect block, 1 doubly-indirect block, and 1 triply-indirect block. The 4.0 BSD and 4.1 BSD versions, and the System V version, used 1,024-byte blocks rather than 512-byte blocks, making the maximum 4,311,812,608 bytes or approximately 4 GiB

a b On-disk structures would support up to 4 GiB , but practical file size is limited by volume size.

^ [8] While FAT32 partitions this large work fine once created, some software won't allow creation of FAT32 partitions larger than 32 GiB . This includes, notoriously, the Windows XP installation program and the Disk Management console in Windows 2000, XP, 2003 and Vista. Use FDISK from a Windows ME Emergency Boot Disk to avoid.

^ The "." and ".." directory entries in HPFS that are seen by applications programs are a partial fiction created by the Installable File System drivers. The on-disk data structure for a directory does not contain entries by those names, but instead contains a special "start" entry. Whilst on-disk directory entries by those names are not physically prohibited, they cannot be created in normal operation, and a directory containing such entries is corrupt.

^ This is the limit of the on-disk structures. The HPFS Installable File System driver for OS/2 uses the top 5 bits of the volume sector number for its own use, limiting the volume size that it can handle to 64 GiB

a b This is the limit of the on-disk structures. The NTFS driver for Windows NT limits the volume size that it can handle to 256 TiB and the file size to 16 TiB respectively.

^ The "classic" Mac OS provides two sets of functions to retrieve file names from an HFS Plus volume, one of them returning the full Unicode names, the other shortened names fitting in the older 31 byte limit to accommodate older applications.

^ HFS Plus mandates support for an escape sequence to allow arbitrary Unicode. Users of older software might see the escape sequences instead of the desired characters.

a b Depends on kernel version and arch. For 2.4 kernels the max is 2 TiB. For 32-bit 2.6 kernels it is 16 TiB. For 64-bit 2.6 kernels it is 8 EiB.

^ [23] ReiserFS has a theoretical maximum file size of 1 EiB , but "page cache limits this to 8 Ti on architectures with 32 bit int"

^ Note that the filename can be much longer XFS#Extended attributes

a b XFS has a limitation under Linux 2.4 of 64 TiB file size, but Linux 2.4 only supports a maximum block size of 2 TiB . This limitation is not present under IRIX

a b QFS allows files to exceed the size of disk when used with its integrated HSM, as only part of the file need reside on disk at any one time.

^ Varies wildly according to block size and fragmentation of block allocation groups.

a b NSS allows files to have multiple names, in separate namespaces.

^ Some namespaces had lower name length limits. "LONG" had an 80-byte limit, "NWFS" 80 bytes, "NFS" 40 bytes and "DOS" imposed 8.3 filename

^ Maximum combined filename/filetype length is 236 bytes; each component has an individual maximum length of 255 bytes.

^ Maximum pathname length is 4,096 bytes, but quoted limits on individual components add up to 1,664 bytes.

^ This restriction might be lifted in newer versions.

a b Sparse files can be larger than the file system size, even though they can't contain more data.

a b Maximum file size on a VMFS volume depends on the block size for that VMFS volume. The figures here are obtained by using the maximum block size.

^ Assuming the typical 2048 Byte sector size. The volume size is specified as a 32 bit value identifying the number of sectors on the volume.

^ Implemented in later versions as an extension

^ Some FAT implementations, such as in Linux, show file modification timestamp (mtime) in the metadata change timestamp (ctime) field. This timestamp is however, not updated on file metadata change.

^ Particular Installable File System drivers and operating systems may not support extended attributes on FAT12 and FAT16. The OS/2 and Windows NT filesystem drivers for FAT12 and FAT16 support extended attributes (using a "EA DATA. SF" pseudo-file to reserve the clusters allocated to them). Other filesystem drivers for other operating systems do not.

^ f-node contains a field for a user identifier. This is not used except by Thecontains a field for a user identifier. This is not used except by OS/2 Warp Server , however.

^ [29] As of Vista, NTFS has support for Mandatory Labels, which are used to enforce Mandatory Integrity Control

^ Initially, ReFS lacked support for ADS, but Server 2012 R2 and up add support for ADS on ReFS

^ Data checksums not enabled by default

a b c d Access-control lists and MAC labels are layered on top of extended attributes.

^ Some operating systems implemented extended attributes as a layer over UFS1 with a parallel backing file (e.g., FreeBSD 4.x).

^ [30] Journal and metadata only

^ Creation time stored since June 2015, xfsprogs version 3.2.3

^ Metadata checksums stored since June 2015, xfsprogs version 3.2.3

a b c d e f The local time, timezone/ UTC offset, and date are derived from the time settings of the reference/single timesync source in the NDS tree.

a b Novell calls this feature "multiple data streams". Published specifications say that NWFS allows for 16 attributes and 10 data streams, and NSS allows for unlimited quantities of both.

a b Some file and directory metadata is stored on the NetWare server irrespective of whether Directory Services is installed or not, like date/time of creation, file size, purge status, etc; and some file and directory metadata is stored in NDS/eDirectory , like file/object permissions, ownership, etc.

^ Record Management Services (RMS) attributes include record type and size, among many others.

^ File permission in 9P are a variation of the traditional Unix permissions with some minor changes, e.g. the suid bit is replaced by a new 'exclusive access' bit.

^ Supported on FreeBSD and Linux implementations, support may not be available on all operating systems.

^ Solaris "extended attributes" are really full-blown alternate data streams, in both the Solaris UFS and ZFS.

^ disabling copy-on-write (COW) to prevent fragmentation also disables checksumming

^ Access times are preserved from the original file system at creation time, but Rock Ridge file systems themselves are read-only.

^ libburnia can backup and restore ACLs with file system creation and extraction programs, but no kernel support exists.

a b libburnia can backup and restore extended attributes and MAC labels with file system creation and extraction programs, but no kernel support exists.

^ System V Release 4, and some other Unix systems, retrofitted symbolic links to their versions of the Version 7 Unix file system, although the original version didn't support them.

^ Context based symlinks were supported in GFS, GFS2 only supports standard symlinks since the bind mount feature of the Linux VFS has made context based symlinks obsolete

^ Optional journaling of data

^ [31] NTFS 3.0 (Windows 2000) and higher can create junctions, which allow entire directories (but not individual files) to be mapped to elsewhere in the directory tree of the same partition (file system). These are implemented through reparse points, which allow the normal process of filename resolution to be extended in a flexible manner. As of Windows Vista, NTFS fully supports symbolic links.NTFS 3.0 (Windows 2000) and higher can create, which allow entire directories (but not individual files) to be mapped to elsewhere in the directory tree of the same partition (file system). These are implemented through, which allow the normal process of filename resolution to be extended in a flexible manner.

a b NTFS stores everything, even the file data, as meta-data, so its log is closer to block journaling.

a b While NTFS itself supports case sensitivity, the Win32 environment subsystem cannot create files whose names differ only by case for compatibility reasons. When a file is opened for writing, if there is any existing file whose name is a case-insensitive match for the new file, the existing file is truncated and opened for writing instead of a new file with a different name being created. Other subsystems like e. g. Services for Unix , that operate directly above the kernel and not on top of Win32 can have case-sensitivity.

^ NTFS does not internally support snapshots, but in conjunction with the Volume Shadow Copy Service can maintain persistent block differential volume snapshots.

^ Supported only on Windows Server SKUs. However, partitions deduplicated on Server can be used on Client.

^ Metadata-only journaling was introduced in the Mac OS X 10.2.2 HFS Plus driver; journaling is enabled by default on Mac OS X 10.3 and later.

^ newfs_hfs -s will create a case-sensitive new file system.[34] HFS Plus version 5 optionally supports case-sensitivity. However, since case-sensitivity is fundamentally different from case-insensitivity, a new signature was required so existing HFS Plus utilities would not see case-sensitivity as a file system error that needed to be corrected. Since the new signature is 'HX', it is often believed this is a new filesystem instead of a simply an upgraded version of HFS Plus.[35][36] Although often believed to be case sensitive, HFS Plus normally is not. The typical default installation is case-preserving only. From Mac OS X 10.3 on the commandwill create a case-sensitive new file system.HFS Plus version 5 optionally supports case-sensitivity. However, since case-sensitivity is fundamentally different from case-insensitivity, a new signature was required so existing HFS Plus utilities would not see case-sensitivity as a file system error that needed to be corrected. Since the new signature is 'HX', it is often believed this is a new filesystem instead of a simply an upgraded version of HFS Plus.

^ [37] Mac OS X Tiger (10.4) and late versions of Panther (10.3) provide file change logging (it's a feature of the file system software, not of the volume format, actually).

^ HFS+ does not actually encrypt files: to implement FileVault , OS X creates an HFS+ filesystem in a sparse, encrypted disk image that is automatically mounted over the home directory when the user logs in.

^ [39][40] Journaled Soft Updates (SU+J) are the default as of FreeBSD 9.x-RELEASE

^ Linux kernel versions 2.6.12 and newer.

a b c Off by default.

^ Full block journaling for ReiserFS was added to Linux 2.6.8.

a b Reiser4 supports transparent compression and encryption with the cryptcompress plugin which is the default file handler in version 4.1.

^ Optionally no on IRIX.

^ Particular Installable File System drivers and operating systems may not support case sensitivity for JFS. OS/2 does not, and Linux has a mount option for disabling case sensitivity.

a b c d Case-sensitivity/Preservation depends on client. Windows, DOS, and OS/2 clients don't see/keep case differences, whereas clients accessing via NFS or AFP may.

a b [44] The file change logs, last entry change timestamps, and other filesystem metadata, are all part of the extensive suite of auditing capabilities built into NDS/eDirectory called NSure Audit.

a b Available only in the "NFS" namespace.

a b These are referred to as "aliases".

^ VxFS provides an optional feature called "Storage Checkpoints" which allows for advanced file system snapshots.

a b ZFS is a transactional filesystem using copy-on-write semantics, guaranteeing an always-consistent on-disk state without the use of a traditional journal. However, it does also implement an intent log to provide better performance when synchronous writes are requested.

^ [45][46] Applies only to proprietary ZFS release and ZFS On Linux. Encryption support is not yet available in whole OpenZFS

a b c Some file system creation implementations reuse block references and support deduplication this way. This is not supported by the standard, but usually works well due to the file system's read-only nature.

a b Variable block size refers to systems which support different block sizes on a per-file basis. (This is similar to extents but a slightly different implementational choice.) The current implementation in UFS2 is read-only.

^ Only for "stuffed" inodes

a b c d Other block:fragment size ratios supported; 8:1 is typical and recommended by most implementations.

^ e2compr , a set of patches providing block-based compression for ext2, has been available since 1997, but has never been merged into the mainline Linux kernel.

a b c Fragments were planned, but never actually implemented on ext2 and ext3.

^ Stores one largest extent in disk, and caches multiple extents in DRAM dynamically.

a b Tail packing is technically a special case of block suballocation where the suballocation unit size is always 1 byte.

^ Each possible size (in sectors) of file tail has a corresponding suballocation block chain in which all the tails of that size are stored. The overhead of managing suballocation block chains is usually less than the amount of block overhead saved by being able to increase the block size but the process is less efficient if there is not much free disk space.

^ Depends on UDF implementation.

a b c Linux supports the zisofs extension that allows per-file compression, and file system creation tools may support creating such images. zisofs images are incompatible on non-Linux OSes.

a b c ISO 9660 Level 3 only