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File Allocation Tables

When preparing a new hard drive for use, there are three different file systems we can use. They are: FAT16, short for File Allocation Table, which is basically an index on your hard drive that allows your computer to remember where your files are located, FAT32, and NTFS, short for NT File System. For most Windows XP users, NTFS is the better choice as it offers security features not found within the other file systems. Therefore, this technical brief will describe in detail the differences between these files systems.


FAT 16 File System

The FAT 16 file system was introduced with MS–DOS and was in use through the first version of Windows 95. It was originally designed to index files on a floppy drive and also on hard drives up to a capacity of 2.1 Gigabytes. Therefore, if you have a 6 GB hard drive you would need to create three individual partitions under FAT 16 to utilize the entire hard drive. In addition, your hard disk is divided into 512-byte pieces called sectors, which are then grouped into larger pieces called clusters. Therefore, the maximum number of clusters that the FAT 16 system can manage is 65,535, and in order to stay within this limit on larger hard disks, the FAT 16 system increases the size of the clusters accordingly. For instance, a 512MB (megabyte) hard disk uses 8KB (kilobyte) clusters, a 850MB hard disk uses 16KB clusters, and a 1.2GB (gigabyte) hard disk uses 32KB clusters and so on.

Therefore, once you get to a 1.2GB hard disk, the size of a cluster grows so large that the storage system becomes very inefficient, especially if you have many small files on your hard disk. No matter how small the file is, it will consume at least one 32KB cluster. For instance, if you store a 1KB file on a 1.2GB hard disk, that small file will take up an entire 32KB of space. The remaining 31KB will be empty. The empty space in a cluster is called slack space. Since the operating system can not write any more data into the slack space, it's completely wasted.

FAT 32 File System

The FAT32 file system was introduced in the second version of Windows 95, often know as Windows 95B or OSR2. It is really just an extension of the original FAT16 file system in order to remain compatible with existing programs, networks, and device drivers. The biggest improvement in FAT 32 is its ability to efficiently manage storage space on today's larger hard drives. It can handle disks larger than 2GB and format them with a single partition thereby allowing you to assign a single drive letter to your drive.

In addition, the FAT 32 file system only uses a 4KB cluster size for all hard disks under 8 Gigabytes. This reduces the amount of slack space found on your hard disk when you save small files to your drive. As mentioned earlier, a 1KB file takes up 32KB of space on a 1GB hard disk using the old FAT 16 file system. However, a 1KB file on the same hard disk using the FAT32 system takes up only 4KB of space, a savings of 28KB. This may sound trivial, but when you are dealing with an entire hard disk that has thousands of files, the savings is actually dramatic and even Microsoft claims that you will achieve at least 10 to 15 percent more efficient use of disk space on the average large hard disk.

FAT32 has some other advantages over the FAT 16 file system in regards to improved reliability. For example, under the FAT 16 file system, the root directory is located only at the beginning of the hard disk. If anything were to happen to this section of the hard disk, such as the development of bad sectors, the whole drive will become unusable as the file index will become damaged. Therefore, one will have to seek out special disk recovery tools to try to recover the data, which more than likely will be unsuccessful. By using the FAT 32 file system, the root directory can be located anywhere on the hard disk. Therefore, if anything happens to the section of the hard disk storing the root directory, the FAT 32 file system's built in utilities will be able to move the root directory to a safe location on the hard disk and repair the defective area. In addition, the FAT 32 file system can use both the default and the backup copy of the File Allocation Table. This means that if something were to happen to the default FAT, your system will continue to run by using the backup copy until the default can be repaired.

NTFS - New Technology File System

The NTFS file system was introduced with the first version of Windows NT (New Technology) and is a completely different file system from FAT 16 and Fat 32. Microsoft actually designed it to be more stable, reliable and offer end users greatly increased security.

Using The FAT And/Or The NTFS File System

If you plan on running more than one operating system on your computer, often referred to Dual Booting, you will definitely need to format some of your volumes with the FAT file system. Any programs or data that need to be accessed by more than one operating system should be stored on the FAT volume(s). But do keep in mind that there is no security for data stored on a FAT16 or FAT32 volume. Therefore, any user with access to the computer, either directly or across a network can read, change, or even delete files that are stored on a FAT16 or FAT32 partition. Therefore, you definitely do want to store any sensitive files on drives or partitions formatted with NTFS file systems.


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