File System Types and Management

Windows Server offers a number of file systems that can be used on media connected to the server. Although you use only one of the file systems for fixed media, you look at all the options.

File Allocation Table (FAT)

File Allocation Table (FAT) is a remnant from the MS-DOS days and was limited to 8.3 filename restrictions until Long File Name (LFN) support was added. Although FAT has been largely replaced by more sophisticated file systems, many media, such as memory cards, still use FAT because of its support across nearly all operating systems.

LFNs worked behind the scenes. The LFN for a file was stored using a series of linked directory entries. An LFN uses one directory entry for its alias (an automatically generated 8.3 name) and a hidden secondary directory entry for every 13 characters in its name. If you had a 200-character filename, it would use 17 entries.

The alias is generated using the first six characters of the LFN, then a ~, and then a number for the first four versions of a files with the same first six characters. For example, for the file mike savills file.txt, the names generated would be mikesa~1.txt, mikesa~2.txt, and so on. After the first four versions of a file, only the first two characters of the filename are used, and the last six are generated, as in jo0E38~1.txt.

FAT is a basic file system. It has no capability to set security on files or audit access. Files on FAT volumes become fragmented because no map is kept of free space on the volume, and FAT has no built-in corruption recovery.

FAT32

Introduced with Windows 95 OSR2, FAT32 is designed to address some of the size limitations of FAT as hard drives increase in size. As with FAT, the same 8.3 filenames exist, although LFN's 255-character filenames are available.