What Is FAT?

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Common FAT Scenarios

This section describes a few scenarios in which the FAT file systems are used.

Mounting a server with a small volume

If you have a small partition (less than 512 megabytes) on a server, the FAT file system imposes the least overhead on a small capacity partition, but still performs well.

Running multiple operating systems

In a multiple-boot configuration with NTFS volumes, you also need a FAT volume if you want to access any of the NTFS volumes from one of the other NTFS volumes. For example, to start a Windows Server 2003-based computer in Microsoft MS-DOS, Microsoft Windows 3.x, or Microsoft Windows 95, you must use FAT16. For a multiple-boot configuration that has Microsoft Windows 95 OEM Service Release 2 (OSR2), Microsoft Windows 98, or Microsoft Windows Millennium Edition (Me), you must use FAT32.

Using FAT with older operating systems

Microsoft Windows 95 and Microsoft Windows 98 use the FAT file system. These operating systems do not support NTFS.

Using FAT with removable disks

For removable disks that can be disconnected or ejected unexpectedly, you must use FAT16 or FAT32.

Operating System and FAT Compatibility

File systems are designed to allow you to format the volume of a hard disk in the way that is most appropriate for your use. Before formatting a volume for a file system, you can determine what the volume will be used for, and which operating system will be mounted on that volume. Sometimes you need to run more than one operating system on your hard disk. The following table shows which FAT file systems are supported by which operating systems.

Operating System and File System Compatibility

Operating System FAT16 FAT32

Windows XP

Table Bullet Table Bullet

Windows Server 2003

Table Bullet Table Bullet

Windows 2000

Table Bullet Table Bullet

Windows NT 4.0

Table Bullet


Windows 95 OSR2, Windows 98, and Windows Me

Table Bullet Table Bullet

Windows 95 (prior to OSR2)

Table Bullet



Table Bullet


Dependencies on Other Technologies

FAT is dependent upon the following technology.

Basic disks and volumes

Basic disks and basic volumes are the storage types most often used with Windows operating systems. The term basic disk refers to a disk that contains basic volumes, such as primary partitions and logical drives. The term basic volume refers to a partition on a basic disk. Basic disks, which are found in both x86-based and Itanium-based computers, provide a simple storage solution that can accommodate changing storage requirements.

FAT is related to the following technology:

NTFS file system

NTFS allows you to gain the maximum benefits for the needs of today’s enterprise business environments from Windows Server 2003, such as increased security, more robust and reliable performance, as well as a design for greater storage growth, features not found in FAT.