ExFAT

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exFAT (Extended File Allocation Table, aka FAT64) is a proprietary file system suited especially for flash drives, introduced by Microsoft for embedded devices in Windows Embedded CE 6.0 and in their desktop operating system, starting with Windows Vista Service Pack 1.^[1] exFAT can be used where the NTFS file system is not a feasible solution, due to data structure overhead.

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

• Scalability to large disk sizes
• Theoretical file size limit of 2⁶⁴ bytes (16 exabytes), limit raised from 2³² bytes (4 gigabytes in FAT32)
• Cluster size of up to 2²⁵⁵ sectors, implementation limit of 32 MB
• Free space allocation and delete performance improved due to introduction of a free space bitmap
• Support for more than 2¹⁶ files in a single directory
• Support for access control lists (not supported yet in Windows Vista SP1)^[2]
• Support for Transaction-Safe FAT File System (TFAT) (optionally WinCE activated function)
• Provision for OEM-definable parameters to customize the file system for specific device characteristics
• Timestamps can finally be in UTC^[3] rather than only local time (starting with Vista SP2)

Additionally, exFAT requires less disk space overhead than NTFS; One reviewer who performed comparative tests found that a 4GB flash drive formatted with NTFS uses 47.2 MB of disk space for overhead, whereas exFAT uses 96 KB.^[4]

The disadvantages compared to previous FAT versions include:

• Devices using exFAT will not be able to use Windows Vista's ReadyBoost capability.^[5]
• Licensing status is unclear. However, Microsoft has previously patented portions of the FAT file system.^[6]
• Not available for previous versions of Microsoft Windows.^[7]
• Not currently available as an open source implementation.

See also

• List of file systems

References

1. ^ Brandon LeBlanc (2007-08-28). "Vista SP1 Whitepaper". Microsoft. Retrieved on 2007-08-28.
2. ^ Anandtech - Second Shot: Windows Vista SP1
3. ^ Mike Nash: Windows Vista Service Pack 2 Beta, The Windows Blog
4. ^ John White. "USB Flash Drive Management". Yoingco.com. Retrieved on 2008-11-01.
5. ^ "exFAT Versus FAT32 Versus NTFS". Retrieved on 2008-07-06.
6. ^ Elizabeth Montalbano (2006-01-11). "Microsoft FAT patents upheld". Computerworld. Retrieved on 2008-02-22.
7. ^ Personal Storage: Opportunities and challenges for pocket-sized storage devices in the Windows world

External links

• Personal Storage: Opportunities and challenges for pocket-sized storage devices in the Windows world (Microsoft PowerPoint presentation)
• TFAT Overview
• Extended FAT File System