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Comparison of file systems
From Wikipedia, the free encyclopedia
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The following tables compare general and technical information for a number of file systems.
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General information
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Metadata
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Features
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File capabilities
Block capabilities
Note that in addition to the below table, block capabilities can be implemented below the file system layer in Linux (LVM, integritysetup, cryptsetup) or Windows (Volume Shadow Copy Service, SECURITY), etc.
Resize capabilities
"Online" and "offline" are synonymous with "mounted" and "not mounted".
Allocation and layout policies
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OS support
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Limits
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While storage devices usually have their size expressed in powers of 10 (for instance a 1 TB Solid State Drive will contain at least 1,000,000,000,000 (1012, 10004) bytes), filesystem limits are invariably powers of 2, so usually expressed with IEC prefixes. For instance, a 1 TiB limit means 240, 10244 bytes. Approximations (rounding down) using power of 10 are also given below to clarify.
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Notes
- 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 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.
- 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.
- The f-node contains a field for a user identifier. This is not used except by OS/2 Warp Server, however.
- NTFS access control lists can express any access policy possible using simple POSIX file permissions (and far more), but use of a POSIX-like interface is not supported without an add-on such as Services for UNIX or Cygwin.
- As of Vista, NTFS has support for Mandatory Labels, which are used to enforce Mandatory Integrity Control.[12]
- Some operating systems implemented extended attributes as a layer over UFS1 with a parallel backing file (e.g., FreeBSD 4.x).
- 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.
- The local time, time zone/UTC offset, and date are derived from the time settings of the reference/single timesync source in the NDS tree.
- 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.
- 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.
- libburnia can back up and restore ACLs with file system creation and extraction programs, but no kernel support exists.
- libburnia can back up 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.
- As of Windows Vista, NTFS fully supports symbolic links.[15] 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.
- 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.
- 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 command newfs_hfs -s will create a case-sensitive new file system.[17] 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.[18][19]
- 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).[20]
- "Soft dependencies" (softdep) in NetBSD, called "soft updates" in FreeBSD provide meta-data consistency at all times without double writes (journaling)
- UDF, LFS, and NILFS are log-structured file systems and behave as if the entire file system were a journal.
- 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.
- 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.[26]
- Bcachefs is a transactional filesystem using copy-on-write semantics, guaranteeing an always-consistent on-disk state without the use of a traditional journal. Journal commits are fairly expensive operations as they require issuing FLUSH and FUA operations to the underlying devices. By default, a journal flush is issued one second after a filesystem update has been done, which primarily records btree updates ordered by when they occurred. This option may be useful on a personal workstation or laptop, and perhaps less appropriate on a server.
- A file system is self-healing if its capable to proactively autonomously detect and correct all but grave errors, faults and corruptions online both in internal metadata AND data. See US7694191B1 as example. This usually requires full checksumming as well as internal redundancy as well as corresponding logic.
- only inside of Stacker 3/4 and DriveSpace 3 compressed volumes[31]
- 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.
- LZJB (optimized for performance while providing decent data compression)
LZ4 (faster & higher ratio than lzjb)
gzip levels: 1 (fastest) to 9 (best), default is 6
zstd positive: 1 (fastest) to 19 (best), default is 3
zstd negative: 1(best & default)-10, 20, 30, …, 100, 500, 1000(fastest)
zle: compresses runs of zeros.[41] - none (default)
The three currently supported algorithms are gzip, LZ4, zstd.
The compression level may also be optionally specified, as an integer between 0 and 15, e.g. lz4:15. 0 specifies the default compression level, 1 specifies the fastest and lowest compression ratio, and 15 the slowest and best compression ratio.[44] - 3.7: Added file-level snapshot (only available in Windows Server 2022).[45]
- By using the per-file "integrity stream" that internally stores a checksum per cluster. Those per cluster checksums are not accessible so it is actually a per file feature and not a per block feature. Integrity streams are not enabled by default.[46]
- With software based on GNU Parted.
- 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.
- Provided in Plan 9 from User Space
- 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; operating systems may also place restrictions of their own, across all filesystems. DOS, Windows, and OS/2 allow only the following characters from the current 8-bit OEM codepage in SFNs: A-Z, 0-9, characters ! # $ % & ' ( ) - @ ^ _ ` { } ~, as well as 0x80-0xFF and 0x20 (SPACE). Specifically, lowercase letters a-z, characters " * / : < > ? \ | + , . ; = [ ], control codes 0x00-0x1F, 0x7F and in some cases also 0xE5 are not allowed.) In LFNs, any UCS-2 Unicode except \ / : ? * " > < | and NUL are allowed in file and directory names across all filesystems. Unix-like systems disallow the characters / and NUL in file and directory names across all filesystems.
- 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 (131.0 KB) 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 (32.76 KB)).
- 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 on-disk structures have no inherent limit. Particular Installable File System drivers and operating systems may impose limits of their own, however. Limited by its Current Directory Structure (CDS), DOS does not support more than 32 directory levels (except for DR DOS 3.31-6.0) or full pathnames longer than 66 bytes for FAT, or 255 characters for LFNs. Windows NT does not support full pathnames longer than 32,767 bytes for NTFS. Older POSIX APIs which rely on the
PATH_MAX
constant have a limit of 4,096 bytes on Linux but this can be worked around. Linux itself has no hard path length limits.[123][124] - Depends on whether the FAT12, FAT16, and FAT32 implementation has support for LFNs. Where it does not, as in OS/2, DOS, Windows 95, Windows 98 in DOS-only mode and the Linux "msdos" driver, file names are limited to 8.3 format of 8-bit OEM 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 must not contain lowercase letters. A few special device names (CON, NUL, AUX, PRN, LPT1, COM1, etc.) should be avoided, as some operating systems (notably DOS, OS/2 and Windows) reserve them.
- While FAT32 partitions this large work fine once created, some software won't allow creation of FAT32 partitions larger than 32 GiB (34.35 GB). 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.[105]
- Depends on CPU arch. For 32bit kernels the max is 16 TiB (17.59 TB). [107]
- Depends on CPU arch. For 32bit kernels the max is 16 TiB (17.59 TB). [108]
- 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.
- 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 (68.71 GB).
- Through the use of multi-extents, a file can consist of multiple segments, each up to 4 GiB (4.294 GB) in size. See ISO 9660#The 2 GiB (2.147 GB) (or 4 GiB (4.294 GB) depending on implementation) file size limit
- 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 (281.4 TB) and the file size to 16 TiB (17.59 TB) respectively; in Windows 10 version 1709, the limit is 8 PiB (9.007 PB) when using 2 MiB (2.097 MB) cluster size.
- 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.
- 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 MB.
- 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 1,024-byte blocks rather than 512-byte blocks, making the maximum 4,311,812,608 bytes or approximately 4 GiB (4.294 GB).
- Note that the filename can be much longer XFS#Extended attributes
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