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exFAT
Developer Microsoft
Full name Extended File Allocation Table
Introduced November 2006 (Windows Embedded CE 6.0)
Partition identifier 0x07 (MBR)
EBD0A0A2-B9E5-4433-87C0-68B6B72699C7 (GPT)
Structures
Directory contents Table
File allocation bitmap, linked list
Bad blocks Cluster tagging
Limits
Max file size 64 ZiB, 512 TiB recommended[1]
Max number of files up to 2,796,202 per directory[2]
Max filename length 255 characters (16-bit)
Max volume size 64 ZiB, 512 TiB recommended[1]
Allowed characters in filenames Unicode UTF-16 except U+0000 (NUL) through U+001F (US) / (slash) \ (backslash) : (colon) * (asterisk) ? (Question mark) " (quote) < (less than) > (greater than) and | (pipe)
Features
Dates recorded Creation, modified, access
Date range January 1, 1980 - December 31, 2107
Date resolution 10 ms
Forks Yes
Attributes Read-only, hidden, system, volume label, subdirectory, archive
File system permissions ACL (WinCE 6 only)
Transparent compression No
Transparent encryption No
Supported operating systems Windows Embedded CE 6.0
Windows XP (including x64) SP2 & later (optional)
Windows Server 2003 requires SP2 (optional)
Windows Vista SP1 & later
Windows 7
Windows Server 2008
Linux

exFAT (Extended File Allocation Table, aka FAT64) is a proprietary, patent-pending[2] file system suited especially for USB flash drives, introduced by Microsoft for embedded devices in Windows Embedded CE 6.0, in their desktop operating systems Windows Vista Service Pack 1[3] and Windows 7, and in their server operating system Windows Server 2008[4].

exFAT can be used where the NTFS file system is not a feasible solution, due to data structure overhead, or where the file size or directory restrictions of previous versions of the FAT file system are unacceptable.

Windows XP and Windows Server 2003 (both x86 and x64) users can add support for exFAT by installing an update from Microsoft.[1] An experimental, open source Linux kernel module that supports the reading of exFAT files is currently under development [5]. A closed source, read/write Linux driver, licensed and derived from the Microsoft exFAT driver, is available for purchase from Tuxera[6].

Contents

Advantages

The advantages over previous File Allocation Table (FAT) file system versions include:

  • Scalability to large disk sizes: 64 ZiB theoretical max, 512 TiB recommended max, raised from the 2 TiB limit of FAT32 partitions. Note that the built-in Windows XP format utility limits new FAT32 partitions to 32 GiB.[1]
  • Sector size between 29 (512) and 212 (4,096) bytes
  • Cluster size up to 32 MiB[1]
  • File size limit of 64 ZiB (512 TiB recommended max), raised from close to 4 GiB in FAT32[1]
  • Free space allocation and delete performance improved due to introduction of a free space bitmap
  • Support for up to 2,796,202 files per directory,[2] increased from 65,536
  • Support for access control lists (not supported yet in Windows Vista SP1)[7]
  • Support for TFAT, a transactional file system standard (optionally WinCE activated function)
  • Provision for OEM-definable parameters to customize the file system for specific device characteristics
  • Support for UTC timestamps (starting with Vista SP2)[8]
  • Timestamp granularity of 10 ms (better than previous FAT versions' 2 s, but worse than NTFS's 100 ns)[2]

Disadvantages

The disadvantages compared to previous FAT versions include:

  • Windows XP and Windows Server 2003 users must have Service Pack 2 or later and install an update to support exFAT
  • Windows Vista must be Service Pack 1 or later for exFAT support
  • Devices formatted using exFAT cannot be read by any version of Windows prior to Windows XP or by any version of DOS or OS/2.
  • Devices using exFAT are unable to use Windows Vista's ReadyBoost capability (Windows 7 adds support for ReadyBoost on exFAT formatted drives and enables a larger ReadyBoost cache due to the removal of the 4GB file size limit of FAT32)[9]
  • Microsoft has not released the official exFAT file specification, and a license from Microsoft is required in order to make and distribute exFAT implementations[10]
  • Limited or no support outside PC environment at present — most current consumer electronics, such as televisions and A/V receivers, can only handle previous FAT versions (this may change with the new SDXC cards and Memory Stick XC requiring exFAT)

Licensing

Companies can integrate exFAT into a specific group of consumer devices, including cameras, camcorders and digital photo frames for a flat fee. Mobile phones, PCs and networks have a different volume pricing model. [11]

See also

References

  1. ^ a b c d e f "KB955704". 2009-01-27. http://support.microsoft.com/?kbid=955704. "Description of the exFAT file system driver update package [for 32-bit XP]"  
  2. ^ a b c d U.S. Patent Application 20090164440  contains Microsoft exFAT specification (revision 1.00)
  3. ^ Brandon LeBlanc (2007-08-28). "Vista SP1 Whitepaper". Microsoft. http://windowsvistablog.com/blogs/windowsvista/pages/windows-vista-service-pack-1-beta-whitepaper.aspx#_Toc175944550. Retrieved 2007-08-28.  
  4. ^ ""Adding Hard Disk Drives"". Microsoft. http://technet.microsoft.com/en-us/library/dd163551.aspx. Retrieved September 15, 2009.  
  5. ^ "Fat64 / exFat fs and Linux". http://groups.google.com/group/fa.linux.kernel/browse_thread/thread/903eb182127e8f21/e2e23eeb3a016268. Retrieved 2009-09-28.  
  6. ^ "Tuxera exFAT for Linux Systems". http://www.tuxera.com/products/exfat-for-embedded-systems/. Retrieved 2009-09-02.  
  7. ^ Anandtech - Second Shot: Windows Vista SP1
  8. ^ Nash, Mike (2008-10-24). "Windows Vista Service Pack 2 Beta". The Windows Blog. http://windowsteamblog.com/blogs/windowsvista/archive/2008/10/24/windows-vista-service-pack-2-beta.aspx. Retrieved 2009-10-02.  
  9. ^ "exFAT Versus FAT32 Versus NTFS". 2008-02-27. http://www.tech-recipes.com/rx/2801/exfat_versus_fat32_versus_ntfs. Retrieved 2009-10-02.  
  10. ^ "exFAT File System Licensing Program". http://www.microsoft.com/iplicensing/productDetail.aspx?productTitle=exFAT%20File%20System%20Licensing%20Program. Retrieved 2009-06-02.  
  11. ^ Marius Oiaga (2009-12-11). "Microsoft Licenses Windows 7’s exFAT Flash File Format". http://news.softpedia.com/news/Microsoft-Licenses-Windows-7-s-exFAT-Flash-File-Format-129512.shtml.  

External links

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