Information about File Systems (Old)

See The Filesystems HOWTO/FAQ for far more detail about many more filesystems than are listed here.

Download a more in-depth version of this document in Word 6/95 format.

PC File Systems

Cluster Size and FAT16

This table excerpted from Technet Article Q67321, below.

                  Drive Size      FAT Type     Sectors     Cluster
               (logical volume)              Per Cluster     Size
               ----------------   --------   -----------   -------

(Floppy Disks)      360K           12-bit         2         1K
                    720K           12-bit         2         1K
                   1.2 MB          12-bit         1       512 bytes
                   1.44 MB         12-bit         1       512 bytes
                   2.88 MB         12-bit         2         1K

(Hard Disks)     0 MB - 15 MB      12-bit         8         4K
                16 MB - 127 MB     16-bit         4         2K
               128 MB - 255 MB     16-bit         8         4K
               256 MB - 511 MB     16-bit        16         8K
               512 MB - 1023 MB    16-bit        32        16K
              1024 MB - 2048 MB    16-bit        64        32K

This means that with a 2 gig partition, a file that is 512 bytes in size takes up 32K of hard drive space. The resulting 31.5k is called "slack space" and is wasted!

Issues with OSR2/FAT32

Editorializing by JP

[...] There are significant incompatibility issues between FAT16 and FAT32. In that respect, use of FAT32 may be compared to use of NTFS. Specifically, most disk utility (Norton) and backup programs will not work. Virus programs, un-installers games and disk compression tools, among others, may also be affected. Users may be better off sticking to the 2gig partition limit and living with slack space.

Windows 98 is also supposed to come with a Fat to FAT32 converter (similar to the NT FAT to NTFS convert.exe) that will do one-way, on-the-fly conversions of FAT to FAT32. And NT 5.0 may support FAT32 volumes, as well as NTFS and FAT.

The following is excerpted from Technet Article Q154997, below.


Compatibility Considerations

In order to maintain the greatest compatibility possible with existing programs, networks, and device drivers, FAT32 was implemented with as little change as possible to Windows 95's existing architecture, internal data structures, Application Programming Interfaces (APIs), and on-disk format. However, because 4 bytes are now required to store cluster values, many internal and on-disk data structures and published APIs have been revised or expanded. In some cases, existing APIs will not work on FAT32 drives. Most programs will be unaffected by these changes. Existing tools and drivers should continue to work on FAT32 drives. However, MS-DOS block device drivers (for example, ASPIDISK.SYS) and disk tools will need to be revised to support FAT32 drives.

All of Microsoft's bundled disk tools (Format, FDISK, Defrag, and MS-DOS- based and Windows-based ScanDisk) have been revised to work with FAT32. In addition, Microsoft is working with leading device driver and disk tool vendors to support them in revising their products to support FAT32.

NOTE: A FAT32 volume cannot be compressed using Microsoft DriveSpace or DriveSpace 3.


Support Boundaries

Microsoft will support the functionality of the FAT32 file system for error- free reading, and saving of files either in real mode or protect mode. We support the real- and protected-mode tools included with Windows 95. Microsoft will not provide support for programs that will not run on the FAT32 file system. For legacy programs that will not install on a FAT32 volume, or will not properly save files or read them, you will have to contact the manufacturer of the software package.

NOTE: Cluster sizes of less than 4K on FAT32 volumes are not supported by Microsoft.


Technet Articles about FAT16 and Cluster Size

  • Q67321 FAT Type and Cluster Size Depends on Logical Drive Size (See above)
  • Q140365 Default Cluster Size for FAT and NTFS
  • Q100108 Overview of FAT, HPFS, and NTFS File Systems
  • Q118335 Maximum Partition Size in MS-DOS
  • Q127851 Problems Accessing Windows FAT Drives Larger than 2 GB
  • Q126855 Windows 95 Support for Large IDE Hard Disks
  • Q120138 Errors Creating Files or Folders in the Root Directory
  • Q39927 MS-DOS: Directory and Subdirectory Limitations
  • Q133248 Microsoft Plus! for Windows 95 Questions and Answers
  • "Long Filename Incompatibility and Administration Issues in Windows 95"
  • "Administrative Considerations for Long Filenames"

Technet Articles about FAT32 and OEM Service Release 2 (OSR2)

  • Q154997 Description of FAT32 File System
  • Q155003 Description of Windows 95 OEM Service Release 2
  • Q152611 OSR2 Cannot Dual-Boot Between Windows 3.x and Windows 95
  • Q152701 FAT32 Using Compatibility Mode with OnTrack Disk Manager
  • Q155366 Error Message Trying to Run OSR2 Compression Agent
  • Q155364 Cannot Boot OSR2 After Booting Previous Operating System
  • Q156331 Cannot Boot OEM Service Release 2 with Windows 95 System Files

PC Magazine:

  • June 25, 1996, pages 217-219 "How Windows 95 Stores Long Filename"
  • July 1996, page 37 "Get ready for Massive Hard Disk"

Other Interesting File Systems