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Understanding File-Size Limits on NTFS and FAT

Don't confuse limits on file size with limits on partition size

In the April 17 Windows Client UPDATE, I wrote about the 4GB file-size limit in FAT32. In response, I've received dozens of email messages telling me that FAT32 isn't limited to 4GB but rather that the 4GB limit is a FAT16 artifact. I also received messages questioning my assertion that NTFS is appropriate for small office/home office (SOHO) and small business users, but my point didn't center on NTFS's general appropriateness. I stand by my conclusion that if you're doing video editing on Windows, you need to use NTFS.

I've run into the 4GB wall when creating files on FAT32 partitions. Because I realized that the problem might have been caused by the video-creation software I was using, I tried again with different software to create an AVI file larger than 4GB. No dice: As soon as the file size reached 4GB, the application failed.

Related:  Maximum file size, volume size, clusters per volume, and number of files per volume for the FAT16, FAT32, and NTFS file systems

With that 4GB figure stuck in my head, I went to my accustomed research tools and found plenty of references to the FAT32 4GB limit. To back up that number, I searched the Microsoft Web site and found numerous articles confirming that the file-size limit on FAT32 is (2^32)-1 bytes, or one byte less than a full 4GB.

The confusion about FAT file size seems to stem from the fact that FAT16 has a 4GB limit on partition size, whereas FAT32 has a 2TB limit on partition size. A large number of my respondents appear to have confused "partition" with "file." To add a little additional confusion, many respondents commented that they're running large drives as one partition on FAT32. In these days of inexpensive 120GB+ hard disks, I guess my definition of "large" differs from that of these readers.

Windows XP and Windows 2000 limit partition creation to no larger than 32GB on FAT32. This limitation is by design: Microsoft wants you to use NTFS for large drives. If you use Windows Me or Windows 98 to format a drive, XP and Win2K can use a FAT32 partition larger than 32GB; however, these OSs can't create the partition. Also, keep in mind that when you use ATA/IDE hard disks larger than 127GB, you might need to update your computer's or hard disk controller's BIOS to properly support those larger drives.

Learn more:  NTFS5 vs. FAT32

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