Data Recovery for FAT 32 :
A version of the file allocation table (FAT) available in Windows 95 OSR 2 and Windows 98. FAT32 increases the number of bits used to address clusters and also reduces the size of each cluster. The result is that it can support larger disks (up to 2 terabytes) and better storage efficiency.
Choosing FAT32 as the file allocation system during the formatting of the hard disk drive will efficiently manage the way the data is stored on the hard disk drive. FAT32 can and should be used for hard disk drives larger than 1.2 GB. Improved hard drive performance using FAT32 on larger hard disk drives is the key advantage of selecting FAT 32 over FAT 16. Before formatting the hard disk drive with FAT 32, the user should verify that all the applications to be installed on the hard disk drive are supported under FAT32. Not all older applications will run under FAT 32. FAT32 is not available under Microsoft Windows NT version 3.51 or 4.0.
Windows 95 OSR2 and Windows 98 include an updated version of the File Allocation Table file system, called FAT32. This updated file system allows for a default cluster size as small as 4K, as well as support for EIDE hard disk sizes in excess of 2 GB.
Every file on your system is stored in clusters on hard drive; the maximum of one file can be stored in a particular cluster, so this results in wastage if the file is under the cluster size. (FAT16) organizes files in 32K clusters in drives over 1.2gig, while FAT32 uses a minimum cluster size of 4K. This means that a 3K file wastes only 1K of disk space on FAT32, while it wastes 29K of space on a standard FAT system. This wastage can result in over 50% of a 2gig drive being wasted.
FAT32 provides the following enhancements over previous implementations of the FAT file system:
- Supports drives up to 2 terabytes in size: Although FAT32 supports drives up to 2 terabytes in size, drives may not be larger than 7.8 GB due to limitations of the BIOS INT13 interface. FAT32 uses smaller clusters (that is, 4K clusters for drives up to 8 GB in size), resulting in 10 to 15 percent more efficient use of disk space relative to large FAT16 drives.
- More robust: FAT32 has the ability to relocate the root directory and use the backup copy of the FAT instead of the default copy. In addition, the boot record on FAT32 drives has been expanded to include a backup of critical data structures. This means that FAT32 drives are less susceptible to a single point of failure than existing FAT16 volumes.
- More flexible: The root directory on a FAT32 drive is now an ordinary cluster chain, so it can be located anywhere on the drive. For this reason, the previous limitations on the number of root directory entries no longer exist. In addition, FAT mirroring can be disabled, allowing a copy of the FAT other than the first one to be active. These features allow for dynamic resizing of FAT32 partitions.
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'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. Existing tools and drivers should continue to work on FAT32 drives. However, MS-DOS block device drivers (for example, ASPIDISK.SYS) and disk tools 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. A FAT32 volume cannot be compressed using Microsoft DriveSpace or DriveSpace.
For most users, FAT32 has a negligible performance impact. Some applications may see a slight performance gain from FAT32. In other applications, particularly those heavily dependent on large sequential write operations, FAT32 may result in modest performance degradation.
If you have more clusters on your hard drive, the slower the performance. This is true for any file system, FAT16, FAT32, NTFS, and HPFS. However, since FAT32 allows for many more clusters on a single partition than FAT16, the effect may be noticeable. Disk utilities are especially affected as there are more clusters in the partition. For instance, the closer to 8GB your partition gets, the more 4K clusters, and the slower the performance.
FAT32 uses the disk cache (Vcache) more efficiently by allowing the memory manager to map directly into memory portions of an application that is in the disk cache. This process eliminates an additional memory copy of the mapped portions of the application. This feature is only available on FAT32 volumes.
FAT32 allows the memory manager to write pageable data very efficiently to the swap file while a system is idle. This feature is only available on FAT32 volumes and volumes with cluster sizes greater than 4K.
Because of the compatibility considerations described above, the implementation of FAT32 involved very little change to Windows 95. The Major differences between FAT32 and earlier implementations of FAT are as follows:
Two new partition types are defined: OxB and OxC. Both indicate FAT32 volumes; type OxC indicates a FAT32 partition that requires extended INTI3 support (LBA).
The boot record on FAT32 drives requires 2 sectors (due to expansion and addition of fields within the BPB). As a result, the number of reserved sectors on FAT32 drives is higher than on FAT16, typically 32. This expanded reserved area allows two complete copies of the boot record to be stored there, as well as a sector in which free space count and other file system information is stored.
The FAT is now larger, because each entry now takes up 4 bytes and there are typically many more clusters than on FAT16 drives.
The root directory is no longer stored in a fixed location. A pointer to the starting cluster of the root directory is stored in the extended BPB. The on-disk format directory entries is unchanged, except that the two bytes previously reserved for Extended Attributes now contain the high order word of the starting cluster number.
Win32 APls are not affected by FAT32, with the exception of one additional API called GetFreeSpaceEx() for determining the true free space on a FAT32 volume.
Creating FAT32 Drives
In OSR2 and Windows 98, if you run the FDISK tool on a system with a drive over 512 MB, it asks whether to enable large disk support. If you answer Yes, any partition you create that is larger than 512 MB is marked as a FAT32 partition.
Windows 98 also includes a FAT32 conversion tool that you can use to convert an existing drive to the FAT32 file system. To use the conversion tool, follow these steps:
- Click Start, point to Programs, point to Accessories, point to System Tools, and then click Drive Converter (FAT32).
- Click Next.
- Click the drive you want to convert to the FAT32 file system, and then click Next.
- Follow the instructions on the screen.