File System ComparisonGeneral information

File system   Creator  Year of

introduction  Original operating

system  DECtape DEC 1964 PDP-6 MonitorLevel-D DEC 1968 TOPS-10V6FS Bell Labs 1972 Version 6 UnixRT-11 DEC 1973 RT-11

Disk Operating System (GEC DOS) GEC 1973 Core Operating System

GEC DOS filing system extended GEC 1977 OS4000

FAT12 Microsoft 1977 Microsoft Disk BASICV7FS Bell Labs 1979 Version 7 UnixODS-2 DEC 1979 OpenVMS

DFS Acorn Computers Ltd 1982 Acorn BBC Micro MOS

FFS Kirk McKusick 1983 4.2BSDMFS Apple Computer 1984 Mac OSHFS Apple Computer 1985 Mac OS

Amiga OFS 54 Metacomco for Commodore 1985 Amiga OSNWFS Novell 1985 NetWare 286

Amiga FFS Commodore 1987 Amiga OS 1.3FAT16 Microsoft 1987 MS-DOS 3.31

Minix V1 FS Andrew S. Tanenbaum 1987 Minix 1.0HPFS IBM & Microsoft 1988 OS/2JFS IBM 1990 AIX 11

VxFS VERITAS 1991 SVR4.0AdvFS DEC Before 1993 Digital Unix

NTFS Microsoft, Gary Kimura, Tom Miller 1993 Windows NT

LFS Margo Seltzer 1993 Berkeley Spriteext2 Rémy Card 1993 Linux

UFS1 Kirk McKusick 1994 4.4BSDXFS SGI 1994 IRIXUDF ISO/ECMA/OSTA 1995 -

FAT32 Microsoft 1996 Windows 95b 10 QFS Sun Microsystems 1996 Solaris

GPFS IBM 1996 AIX,Linux

Be File System Be Inc., D. Giampaolo, C. Meurillon 1996 BeOS

Minix V2 FS Andrew S. Tanenbaum 1997 Minix 2.0HFS Plus Apple 1998 Mac OS 8.1

NSS Novell 1998 NetWare 5PolyServe File System

(PSFS) PolyServe 1998 Windows, Linux

ODS-5 DEC 1998 OpenVMS 7.2

ext3 Stephen Tweedie 1999 LinuxJFS2 IBM 1999 OS/2 WSeBGFS Sistina (Red Hat) 2000 Linux

ReiserFS Namesys 2001 LinuxFATX Microsoft 2002 XboxUFS2 Kirk McKusick 2002 FreeBSD 5.0OCFS Oracle Corporation 2002 Linux

VMFS2 VMware 2002 ESXFossil Bell Labs 2003 Plan 9 from Bell Labs 4

Google File System Google 2003 LinuxZFS Sun Microsystems 2004 Solaris

Reiser4 Namesys 2004 LinuxMinix V3 FS Andrew S. Tanenbaum 2005 MINIX 3

OCFS2 Oracle Corporation 2005 LinuxNILFS NTT 2005 LinuxVMFS3 VMware 2005 ESXGFS2 Red Hat 2006 Linuxext4 Andrew Morton 2006 Linux

exFAT Microsoft 2006 Windows CE 6.0

File system Creator Year of introduction Original operating system

Limits

  

Maximum

filename length  

Allowable characters

in directory entries25  

Maximum pathname length  Maximum file

size  

Maximum volume size 4  

DECtape 6.3 A-Z, 0-9 DTxN:FILNAM.EXT = 15 369,280 bytes (577 * 640)

369,920 Bytes (578

* 640)

Level-D 6.3 A-Z, 0-9DEVICE:FILNAM.EXT[PROJCT,PROGRM] = 7 + 10 + 15 = 32; + 5*7 for SFDs =

67

34,359,738,368 words (2**35-

1); 206,158,430,208 SIXBIT bytes

Approx 12 GB (64 * 178MB)

RT-11 12 bytes A-Z, 0-9, $ 16 bytes33,554,432

bytes (65536 * 512)

33,554,432 Bytes

V6FS 14 bytes 24

Any byte except

NUL and / 26

No limit defined 12 8MiB 57 2TiB

Disk Operating

System (GEC DOS)

 ?  ?  ?  ? at least 131072 bytes  ?

GEC 8 bytes A-Z, 0-9.  ? No limit defined (workaround for OS  ? at least  ?

DOS filing

system extended

Period was directory separator

limit) 131072 bytes

V7FS 14 bytes 24

Any byte except

NUL and / 26

No limit defined 12 1GiB 58 2TiB

FAT12 255 bytes 24

Any Unicode except

NUL 24 26

No limit defined 12 32MiB 1MiB to 32MiB

FAT16 255 bytes 24

Any Unicode except

NUL 24 26

No limit defined 12 2GiB 16MiB to 4GiB

FATX 42 bytes 24

ASCII. Unicode

not permitted.

No limit defined 12 2GiB 16MiB to 2GiB

Fossil  ?  ?  ?  ?  ?

MFS 255 bytes Any byte except : No path (flat filesystem) 256MiB 256MiB

HFS 31 bytes Any byte except : Unlimited 2GiB 2TiB

FAT32 255 bytes 24

Any Unicode except

NUL 24 26

No limit defined 12 4GiB 512MiB to 2TiB 7

HPFS 255 bytesAny byte

except NUL 27

No limit defined 12 2GiB 2TiB 13

NTFS254

characters + "."

Any Unicode except

NUL, / or :

32,767 Unicode characters with each path component (directory or filename) up to

255 characters long 1216EiB 55 16EiB 55

HFS Plus

255 UTF-16

characters 1

Any valid Unicode 2 26 Unlimited 16EiB 16EiB 71

FFS 255 bytesAny byte

except NUL 26

No limit defined 12 4GiB 256TiB

UFS1 255 bytesAny byte

except NUL 26

No limit defined 12 4GiB to 256TiB 256TiB

UFS2 255 bytesAny byte

except NUL 26

No limit defined 12 512GiB to 32PiB 1YiB

ext2 255 bytesAny byte

except NUL 26

No limit defined 12 16GiB to 2TiB 4 2TiB to 32TiB

ext3 255 bytes Any byte No limit defined 12 16GiB to 2TiB 4 2TiB to

except NUL 26 32TiB

ext4Any byte

except NUL 26

No Limit defined 12 16GiB to 2TiB 4 1024 PiB

GPFS 255 (?)Any byte

except NUL 26

No limit defined 12 No limit found299 Bytes

(2PiB tested)

GFS 255Any byte

except NUL 26

No limit defined 12 2TB to 8EB 63 2TB to 8EB 63

ReiserFS4032

bytes/255 characters

Any byte except NUL 26

No limit defined 12 8TiB 8 (v3.6), 4GiB (v3.5) 16TiB

Reiser4 3976 bytesAny byte

except / and NUL

No limit defined 12 8TiB on x86  ?

OCFS 255 bytesAny byte

except NUL 26

No limit defined 12 8TiB 8TiB

OCFS2 255 bytesAny byte

except NUL 26

No limit defined 12 4PiB 4PiB

XFS 255 bytesAny byte

except NUL 26

No limit defined 12 8EiB 9 8EiB 9

JFS 255 bytesAny byte

except NUL 26

No limit defined 12 8EiB 512TiB to 4PiB

JFS2 255 bytes

Any Unicode except NUL

No limit defined 12 4PiB 32PiB

QFS 255 bytesAny byte

except NUL 26

No limit defined 12 16EiB 72 4PiB 72

BFS 255 bytesAny byte

except NUL 26

No limit defined 12 12288 bytes to 260GiB 3

256PiB to 2EiB

AdvFS 255 characters

Any byte except NUL 26

No limit defined 12 16TiB 16TiB

NSS 256 characters

Depends on namespace

used 28Only limited by client 8TiB 8TiB

NWFS 80 bytes 52Depends on namespace

used 28No limit defined 12 4GiB 1TiB

ODS-5 236 bytes15  ? 4096 bytes16 1TiB 1TiB

VxFS 255 bytesAny byte

except NUL 26

No limit defined 12 16EiB  ?

UDF 255 bytes

Any Unicode except NUL

1023 bytes 43 16EiB  ?

ZFS 255 bytes

Any Unicode except NUL

No limit defined 12 16EiB268EiB (2128

Bytes)

Minix V1 FS

14 or 30 bytes, set

at filesystem creation

time

Any byte except NUL 26

No limit defined 12 1GiB 1GiB

Minix V2 FS

14 or 30 bytes, set

at filesystem creation

time

Any byte except NUL 26

No limit defined 12 1GiB 1GiB

Minix V3 FS 60 bytes

Any byte except NUL 26

No limit defined 12 4GiB 4GiB

VMFS2 128

Any byte except

NUL and / 26

2048 4TiB 74 64TiB

VMFS3 128

Any byte except

NUL and / 26

2048 2TiB 74 64TiB

Maximum

filename length

Allowable characters

in directory entries25

Maximum pathname length Maximum file size

Maximum volume

size 4

Metadata

  

Stores file

owner  

POSIX file permission

s  

Creation timestamp

s  

Last access/rea

d timestamp

s  

Last metadata change

timestamps  

Last archive

timestamps  

Access

control

lists  

Security/

MAC labels  

Extended

attributes/

Alternate data stream

s/ forks  

Checksum/

ECC  

GPFS Yes Yes Yes Yes Yes No Yes Yes Yes YesDECta

pe No No Yes No No No No No No No

Level- Yes Yes Yes Yes Yes Yes Yes No No No

DRT-11 No No No Yes Yes No No No No NoV6FS Yes Yes No Yes Yes No No No No NoV7FS Yes Yes No Yes Yes No No No No No

FAT12 No No Yes Yes No[1] No No No No 22 NoFAT16 No No Yes Yes No[1] No No No No 22 NoFAT32 No No Yes Yes No[1] No No No No NoHPFS Yes14 No Yes Yes No No No  ? Yes NoNTFS Yes No5 Yes Yes Yes No Yes  ? Yes NoHFS No No Yes No No Yes No No Yes NoHFS Plus Yes Yes Yes Yes Yes Yes Yes  ? Yes No

FFS Yes Yes No Yes Yes No No No No No

UFS1 Yes Yes No Yes Yes No Yes 33 Yes 33 No 32 No

UFS2 Yes Yes Yes Yes Yes No Yes 33 Yes 33 Yes No

LFS Yes Yes No Yes Yes No No No No No

ext2 Yes Yes No Yes Yes No Yes 23 Yes 23 Yes No

ext3 Yes Yes No Yes Yes No Yes 23 Yes 23 Yes No

ext4 Yes Yes No Yes Yes No Yes 23 Yes 23 Yes No

GFS Yes Yes No Yes Yes No Yes 23 Yes 23 Yes No

ReiserFS Yes Yes No Yes Yes No Yes

23 Yes 23 Yes No

Reiser4 Yes Yes No Yes Yes No No No No No

OCFS No Yes No No Yes Yes No No No NoOCFS

2 Yes Yes No Yes Yes No No No No No

XFS Yes Yes No Yes Yes No Yes Yes 23 Yes NoJFS Yes Yes Yes Yes Yes No Yes Yes Yes NoQFS Yes Yes Yes Yes Yes Yes Yes No Yes NoBFS Yes Yes Yes No No No No No Yes No

AdvFS Yes Yes No Yes Yes No Yes No Yes NoNSS Yes Yes Yes31 Yes31 Yes Yes31 Yes  ? Yes19 29 No

NWFS Yes  ? Yes31 Yes31 Yes Yes31 Yes  ? Yes19 29 NoODS-5 Yes Yes Yes  ?  ? Yes Yes  ? Yes 17 NoVxFS Yes Yes Yes Yes Yes No Yes  ? Yes 23 NoUDF Yes Yes Yes Yes Yes Yes Yes No Yes NoFossil Yes Yes 61 No Yes Yes No No No No NoZFS Yes Yes Yes Yes Yes Yes Yes No 69 Yes 60 Yes

VMFS2 Yes Yes No Yes Yes No No No No No

VMFS3 Yes Yes No Yes Yes No No No No No

Stores file

POSIX file permission

Creation timestamp

Last access/rea

Last metadata

Last archive

Access

Security/

Extended

Checksum/

owner s sd

timestamps

change timestamp

s

timestamps

control

lists

MAC labels

attributes/

Alternate data streams/ forks

ECC

Features   Hard

links  Soft

links  Block

journaling

or  

Metadata-only

journaling  

Case-sensitive 

 

Case-preservin

g  

File Chan

ge Log  

Internal snapshotting/branc

hing  

XIP   Filesystem-level

encryption  

DECtape No No No No No No No No No No

Level-D No No No No No No No No No No

RT-11 No No No No No No No No No NoV6FS Yes No No No Yes Yes No No No NoV7FS Yes No 59 No No Yes Yes No No No No

FAT12 No No No No No No No No No NoFAT16 No No No No No Partial No No No NoFAT32 No No No No No Partial No No No NoHPFS No No No No No Yes No  ? No NoNTFS Yes Yes34 No37 Yes37 Yes36 Yes Yes Yes  ? YesHFS Plus

Partial Yes No Yes48 Partial35 Yes Yes64 No No No77

FFS Yes Yes No No Yes Yes No No No NoUFS1 Yes Yes No No Yes Yes No No No NoUFS2 Yes Yes No No66 Yes Yes No Yes  ? NoLFS Yes Yes Yes38 No Yes Yes No Yes No Noext2 Yes Yes No No Yes Yes No No Yes65 Noext3 Yes Yes Yes 62 Yes Yes Yes No No  ? Noext4 Yes Yes Yes 62 Yes Yes Yes No No  ? No

ReiserFS Yes Yes Yes 44 Yes Yes Yes No No  ? No

Reiser4 Yes Yes Yes No Yes Yes No  ?  ? Yes 50

OCFS No Yes No No Yes Yes No No No NoOCFS

2 Yes Yes Yes Yes Yes Yes No No No No

XFS Yes Yes No Yes Yes 40 Yes Yes No  ? NoJFS Yes Yes No Yes Yes30 Yes No  ?  ? NoQFS Yes Yes No No Yes Yes No No No No

Be File Syste

mYes Yes No Yes Yes Yes  ?  ? No No

NSS Yes Yes  ? Yes Yes20 Yes20 Yes6 Yes No YesNWFS Yes53 Yes53 No No Yes20 Yes20 Yes6  ? No No

ODS-2 Yes Yes18 No Yes No No Yes Yes No NoODS-5 Yes Yes18 No Yes No Yes Yes Yes  ? NoUDF Yes Yes Yes38 Yes38 Yes Yes No No Yes NoVxFS Yes Yes Yes No Yes Yes Yes Yes70  ? NoFossil No No No No Yes Yes Yes Yes No NoZFS Yes Yes Yes56 No56 Yes Yes No Yes No No

VMFS2 Yes Yes No Yes Yes Yes No No No No

VMFS3 Yes Yes No Yes Yes Yes No No No No

Hard links

Soft links

Block journaling or

Metadata-only

journaling

Case-sensitive

Case-preservin

g

File Chan

ge Log

Internal snapshotting/branc

hing

XIP Filesystem-level

encryption

Allocation and layout policies

  Tail

packing  Transparent

compression  Block

suballocation  

Allocate-on-flush   Extents  

Variable file block size 41  

Sparse files  

DECtape No No No No No No NoLevel-D No No Yes No Yes No NoV6FS No No No No No No NoV7FS No No No No No No No

FAT12 No No 51 No No No No NoFAT16 No No 51 No No No No NoFAT32 No No No No No No NoHPFS No No No No Yes No NoNTFS No Yes Partial No Yes No Yes

HFS Plus No No No No Yes No YesFFS No No 8:1 45 No No No  ?

UFS1 No No 8:1 45 No No No YesUFS2 No No 8:1 45 No No Yes YesLFS No No 8:1 45 No No No Yesext2 No No 49 No 47 No No No Yesext3 No No No 47 No No No Yesext4 No No No 47 Yes Yes No Yes

ReiserFS Yes No Yes 73 No No No YesReiser4 Yes Yes 50 Yes 73 Yes Yes 39 No YesOCFS No No No No Yes No  ?OCFS2 No No No No Yes No Yes

XFS No No No Yes Yes No YesJFS No No Yes No Yes No YesQFS No No Yes No No No  ?BFS No No No No Yes No  ?NSS No Yes No No Yes No  ?

NWFS No Yes Yes 42 No No No  ?ODS-5 No No No No Yes No  ?VxFS No No  ? No Yes No Yes

UDF No No No  ? 46 Yes No NoFossil No Yes No No No No  ?ZFS Partial 68 Yes  ? Yes 67 No Yes  ?

VMFS2 No No Yes No No No YesVMFS3 No No Yes No No No Yes

Tail packing

Transparent compression

Block suballocation

Allocate-on-flush Extents

Variable file block

size 41

Sparse files

NotesNote 1: The Mac OS provides two sets of functions to retrieve file names from a 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.Note 2: 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.Note 3: Varies wildly according to block size and fragmentation of block allocation groups.Note 4: 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 128KiB 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 32KiB).Note 5: NTFS access control lists can express essentially any access policy possible using simple POSIX file permissions, but use of a POSIX-like interface is not supported without an add-on such as Services for UNIX or Cygwin.Note 6: 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. (Filesystem Events tracked by NSure)Note 7: While FAT32 partitions this large work fine once created, some software won't allow creation of FAT32 partitions larger than 32GiB. 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. [1]Note 8: ReiserFS has a theoretical maximum file size of 1EiB, but "page cache limits this to 8 Ti on architectures with 32 bit int"[2]Note 9: XFS has a limitation under Linux 2.4 of 64TiB file size, but Linux 2.4 only supports a maximum block size of 2TiB. This limitation is not present under IRIX.Note 10: Microsoft first introduced FAT32 in Windows 95 OSR2 (OEM

Service Release 2) and then later in Windows 98. NT-based Windows did not have 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.Note 11: IBM introduced JFS with the initial release of AIX Version 3.1 in 1990. This file system now called JFS1. The new JFS (sometimes called JFS2), on which the Linux port was based, was first shipped in OS/2 Warp Server for e-Business in 1999.Note 12: The on-disk structures have no inherent limit. Particular Installable File System drivers and operating systems may impose limits of their own, however. MS-DOS does not support full pathnames longer than 260 bytes for FAT12 and FAT16. Windows NT does not support full pathnames longer than 32767 bytes for NTFS.Note 13: 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 64GiB.Note 14: The f-node contains a field for a user identifier. This is not used except by OS/2 Warp Server, however.Note 15: Maximum combined filename/filetype length is 236 bytes; each component has an individual maximum length of 255 byes.Note 16: Maximum pathname length is 4096 bytes, but quoted limits on individual components add up to 1664 bytes.Note 17: Record Management Services (RMS) attributes include record type and size, among many others.Note 18: These are referred to as "aliases".Note 19: 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.Note 20: 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.Note 21: Published specs say that the 128-bit file system provides for up to 264 bytes to describe the file system, file size, directory entries, etc, with a theoretical max of 2128 bytes total to describe all storage on such a machine.Note 22: 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.Note 23: Some Installable File System drivers and operating systems may not support extended attributes, access control lists or security labels on these filesystems. Linux kernels prior to 2.6.x may either be missing support for these altogether or require a patch.

Note 24: Depends on whether the FAT12, FAT16, and FAT32 implementation has support for LFNs. Where it does not, as in OS/2, MS-DOS, Windows 95, Windows 98 in DOS-only mode and the Linux "msdos" driver, file names are limited to 11 8-bit characters (space padded in both the basename and extension parts) and may not contain NUL (end-of-directory marker) or character 5 (replacement for character 229 which itself is used as deleted-file marker). Short names also do not normally contain lowercase letters. Also note that a few special names (CON, NUL, LPT1) should be avoided, as some operating systems (notably DOS and windows) effectively reserve them.Note 25: These are the restrictions imposed by the on-disk directory entry structures themselves. Particular Installable File System drivers may place restrictions of their own on file and directory names; and particular and operating systems may also place restrictions of their own, across all filesystems. MS-DOS, Microsoft Windows, and OS/2 disallow the characters \ / : ? * " > < | and NUL in file and directory names across all filesystems. Unices and Linux disallow the characters / and NUL in file and directory names across all filesystems.Note 26: 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.Note 27: 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.Note 28: NSS allows files to have multiple names, in separate namespaces.Note 29: 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.Note 30: 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.Note 31: The local time, timezone/UTC offset, and date are derived from the time settings of the reference/single timesync source in the NDS tree.Note 32: Some operating systems implemented extended attributes as

a layer over UFS1 with a parallel backing file (e.g., FreeBSD 4.x).Note 33: Access-control lists and MAC labels are layered on top of extended attributes.Note 34: As of Windows Vista, NTFS fully supports soft links. See this Microsoft article on Vista kernel improvements. 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.Note 35: Although often believed to be case sensitive, HFS Plus normally is not. The typical default installation is case-preserving only. From Mac OS 10.3 on the command newfs_hfs -s will 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. See Apple's File System Comparisons (which hasn't been updated to discuss HFSX) and Technical Note TN1150: HFS Plus Volume Format (which provides a very technical overview of HFS Plus and HFSX).Note 36: 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.Note 37: NTFS stores everything, even the file data, as meta-data, so its log is closer to block journaling.Note 38: UDF and LFS are log-structured file systems and behave as if the entire file system were a journal.Note 39: In "extents" mode.Note 40: Optionally no on IRIX.Note 41: 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.Note 42: 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.Note 43: This restriction might be lifted in newer versions.Note 44: Full block journaling for ReiserFS was added to Linux 2.6.8.Note 45: Other block:fragment size ratios supported; 8:1 is typical and recommended by most implementations.Note 46: Depends on UDF implementation.Note 47: Fragments were planned, but never actually implemented on ext2 and ext3.Note 48: Metadata-only journaling was introduced in the Mac OS 10.2.2 HFS Plus driver; journaling is enabled by default on Mac OS 10.3 and later.Note 49: 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.Note 50: Reiser4 supports transparent compression and encryption with the cryptcompress plugin which is the default file handler in version 4.1.Note 51: DoubleSpace in DOS 6, and DriveSpace in Windows 95 and Windows 98 were data compression schemes for FAT, but are no longer supported by Microsoft.Note 52: Some namespaces had lower name length limits. "LONG" had an 80-byte limit, "NWFS" 80 bytes, "NFS" 40 bytes and "DOS" imposed 8.3-style names.Note 53: Available only in the "NFS" namespace.Note 54: Metacomco released a so called "evolution" version of original file system that was previously designed by engineers of Amiga Corporation (Formerly Hi-Toro) in 1982-83/85. Unfortunately, Metacomco made a mess of the early FS ruining its simple and easy structure. Originally OFS was simply Amiga File System. Name changed since the release of the "new" Fast File System, born in 1987 for the same platform.Note 55: This is the limit of the on-disk structures. The NTFS driver for Windows NT limits the volume size that it can handle to 256TiB and the file size to 16TiB respectively.Note 56: 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.Note 57: 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.Note 58: 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 4.0BSD and 4.1BSD versions, and the System V

version, used 1024-byte blocks rather than 512-byte blocks, making the maximum 4,311,812,608 bytes or approximately 4 GiB.Note 59: 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.Note 60: Solaris "extended attributes" are really full-blown alternate data streams, in both the Solaris UFS and ZFS.Note 61: File permission in 9P are a variation of the traditional Unix permissions with some minor changes, eg. the suid bit is replaced by a new 'exclusive access' bit.Note 62: Off by default.Note 63: Depends on kernel version and arch. For 2.4 kernels the max is 2TB. For 32-bit 2.6 kernels it is 16TB. For 64-bit 2.6 kernels it is 8EB.Note 64: Mac OS 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). See fslogger.Note 65: Linux kernel versions 2.6.12 and newer.Note 66: "Soft dependencies" (softdep) in NetBSD, called "soft updates" in FreeBSD provide meta-data consistency at all times without double writes (journaling).Note 67: Due to its use of copy on write, ZFS uses delayed allocation for all writes.Note 68: When enabled, ZFS's logical-block based compression behaves much like tail-packing for the last block of a file.Note 69: MAC/Sensitivity labels in the file system are not out of the question as a future compatible change but aren't part of any available version of ZFS.Note 70: VxFS provides an optional feature called "Storage Checkpoints" which allows for advanced file system snapshots.Note 71: While the volume size of HFS+ is almost unlimited, the Mac OS has those limitations: Mac OS 8 & 9: 2 TiB; Mac OS X 10 & 10.1: 2 TiB; Mac OS X 10.2: 8 TiB; Mac OS X 10.3 & 10.4: 16 TiB. Max. file size is slightly smaller than max. volume size (Mac OS 8: max. file size: 2 GiB). Max. number of files (or folders) within a folder: Mac OS 8 & 9: 2^15 (32767), Mac OS X: 2^31, but naturally limited by the max. volume size divided by the block size.Note 72: 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.Note 73: Tail packing is technically a special case of block suballocation where the suballocation unit size is always 1 byte.Note 74: 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.Note 76: VMFS transactions are atomic across the entire distributed cluster.

Note 77: 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.

1. ^ a b c 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.