Every computer we use today almost always has a hard drive. I’m not sure how else you could run one, quite frankly. Hard Drives store information on little platters, which are shaped like Frisbees, but made of metal and coated with a magnetic substance. But how exactly is the data organized on those little platters? They do it with a thing called a file system. File systems are mostly operating system dependent. This means that almost every operating system has a different type of file system. Windows is the most widely used operating system in the United States and Europe, so Windows-compatible file systems are pretty much the standard that most other operating systems can at least read from.

FAT

The Dos/Windows file system is called File Allocation Table, or just FAT for short.  There are 3 types of this FAT file system:

• FAT12. An old 12-bit file system which is mainly used on floppy disks and REALLY small hard drives.


• FAT16. A 16-bit file system used by DOS-based machines as well as PCs using older versions of Windows such as 3.x. Windows 9x is FAT16 compatible, but by this time FAT32 was becomining the new norm.


• FAT32. A 32-bit file system most common today.

Whether a partition is going to use FAT12 or FAT16 is based mainly on it’s size and version of DOS you are using.  If the partition or disk is 16MB or less in size, it is going to use FAT12.  If the partition is between the size of 17MB and 2048MB, it will use the FAT16 file system.

FAT uses clusters to store files in. Each cluster is a group of sectors. The computer gives each cluster it’s own address, just as each house in a neighborhood has it’s own address. The operating system then keeps track of which files are stored in which clusters. The cluster size is determined by the partition size as well as the type of FAT system being used.  The cluster size is important because only one file can be stored in a cluster at a time. If you have a cluster that is 32KB, and you are storing a file in it that is only 1KB, you are wasting 31KB of space on your hard drive.  That’s not very big when you look at it in terms of a 2GB hard drive which has 2,097,152KB on the drive, but when you take a look and realize that there are no files that are perfectly going to fill up 32KB, you are wasting space with every file you have on your hard drive. How can this be avoided?   The smaller the partition you have, the smaller the clusters you will have, and the less wasted space you will have.  Below is a table showing the exact cluster sizes you will get with partition sizes.

There is a slight problem with the FAT16 file system. What would you do if you had a hard drive larger than 2GB and wanted only 1 partition?  FAT32 solved that. It now supports drives up to 2048GB. 2048GB = 2 terabytes. FAT32 also solved the problem of large cluster sizes. Below is another table, but this compares the size of a FAT32 with it’s cluster sizes.

Unfortunately, the ability to make a 260MB FAT32 partition is limited due to the fact that the major program that makes partitions limits FAT32 drives to 512MB. The improved nature of FAT32 has caused this file system to be the most common type used. All later versions of Windows either work primarily with this file system or at least support it (like Windows 2000 and XP, which both allow FAT32 as an option over NTFS). On version of Windows supporting both FAT16 and FAT32, Microsoft usually bundles a conversion utility with the operating system to allow you to convert a FAT16 partition to a FAT32 partition without data loss.

NTFS

NTFS (NT File system) is the major file system used by Microsoft’s Windows NT, 2000 and XP. (Each of these also support the FAT file system). NTFS has features to improve reliability, such as transaction logs to help recover from disk failures. To control access to files, you can set permissions for directories and/or individual files. NTFS files are not accessible from other OSs such as DOS

For large applications, NTFS supports spanning partitions or volumes which means files and directories can be spread out across several physical disks. This file system is mainly used by the corporate and power users.

HPFS
High Performance File system is basically a mix between NTFS and FAT. While FAT offers the 8.3 file naming system (8 characters, then a dot, then 3 more characters) HPFS will support up to 256 characters in a file name.  This file system is mainly used by OS/2, which was IBM’s answer to Microsoft Windows.

Ext2
Ext2 is a file system used by Linux.  The main people that use it are those that run the many versions of the Linux Operating system.

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