ExFAT
| Developer(s) | Microsoft |
|---|---|
| Full name | Extended File Allocation Table |
| Introduced | November 2006 with Windows Embedded CE 6.0 |
| Partition identifier |
MBR/EBR: 0x07 (same as for HPFS/NTFS) BDP/GPT: EBD0A0A2-B9E5-4433-87C0-68B6B72699C7 |
| Structures | |
| Directory contents | Table |
| File allocation | bitmap, linked list |
| Bad blocks | Cluster tagging |
| Limits | |
| Max. volume size | ca. 128 PiB, 512 TiB recommended |
| Max. file size | ca. 128 PiB (theoretical 16 EiB–1) |
| Max. number of files | up to 2,796,202 per directory |
| Max. filename length | 255 UTF-16 characters |
| 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, last access |
| Date range | 1980-01-01 to 2107-12-31 |
| Date resolution | 10 ms |
| Forks | No |
| Attributes | Read-only, hidden, system, subdirectory, archive |
| File system permissions | ACL (Windows CE 6 only) |
| Transparent compression | No |
| Transparent encryption | No |
| Other | |
| Supported operating systems |
Windows Embedded CE 6.0 Windows XP (including x64) SP2 and later (optional) Windows Server 2003 SP2 (optional) Windows Vista SP1 and later Windows 7 Windows 8 Windows 10 Windows Server 2008 Windows Server 2008 R2 Linux (via FUSE or non-mainline kernel driver) Mac OS X 10.6.5 and later Some Android OS devices such as the Sony Xperia Z (running the latest firmware) |
exFAT (Extended File Allocation Table) is a Microsoft file system optimized for flash memory such as USB flash drives and SD cards. It is proprietary and Microsoft owns patents on several elements of its design.
exFAT can be used where the NTFS file system is not a feasible solution (due to data structure overhead), yet the file size limit of the standard FAT32 file system is unacceptable.
exFAT has been adopted by the SD Card Association as the default file system for SDXC cards larger than 32 GiB.
exFAT was first introduced in late 2006 as part of Windows CE 6.0, an embedded Windows operating system. Most of the vendors signing on for licenses of exFAT are either for embedded systems or device manufacturers that produce media that will be preformatted with exFAT. The entire File Allocation Table (FAT) family, exFAT included, is used for embedded systems because it is lightweight and is better suited for solutions that have low memory and low power requirements, and can be implemented in firmware.
exFAT allows individual files larger than 4 GiB, facilitating long continuous recording of HD video which can exceed the 4 GiB limit in less than an hour. Current digital cameras using FAT32 will break the video files into multiple segments of approximately 2 or 4 GiB. With the increase of capacity and the increase of data being transferred, the write operation needs to be made more efficient. SDXC cards, running at UHS-I have a minimum guaranteed write speed of 10 MBps and exFAT plays a factor in achieving that throughput through the reduction of the file system overhead in cluster allocation. This is achieved through the introduction of a cluster bitmap and elimination (or reduction) of writes to the FAT table. A single bit in the directory record indicates that the file is contiguous, telling the exFAT driver to ignore the FAT table. This optimization is analogous to an extent in other file systems, except that it only applies to whole files, as opposed to contiguous parts of files.
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