How to choose between File Systems - Fat or NTFS

[James Afflek]

Hard disc partitions

The mechanism that allows you to install several operating systems on a single PC or to carve up a single physical disc drive into multiple “logical” disc drives is called partitioning.

Partitioning is performed by special applications. In MS-DOS and Windows, these are FDISK and Disk Management.

Partitioning programs perform the following:

• create a primary partition

• create an extended partition that can be split into several logical discs

• set an active partition (applied to a single primary partition only)

Information about partitions on a hard disc is stored in a special disc area – in the 1st sector of cylinder 0, header 0, which is called the partition table. This sector is called the master boot record, or MBR.

A physical hard disc might contain up to four partitions. This limit is forced by the partition table that is suitable for four strings only. However, this does not mean you can have only four operating systems on your PC! Applications called disc managers support far more operating systems on discs.


File systems

An operating system gives the user the ability to work with data by supporting some type of file system on a partition.

All file systems are made of structures that are necessary to store and manage data. These structures are usually composed of operating system boot sectors, folders and files. File systems perform the following basic functions:

• track occupied and free disc space (and bad sectors, if any)

• support folders and file names

• track physical location of files on discs

Different operating systems use different file systems. Some operating systems are able to work with only one file system while others can use several of them. Here are some of the most widely used file systems:


What's FAT?

FAT may sound like a strange name for a file system, but it's actually an acronym for File Allocation Table. Introduced in 1981, FAT is ancient in computer terms. Because of its age, most operating systems, including Microsoft Windows NT®, Windows 98, the Macintosh OS, and some versions of UNIX, offer support for FAT.


1) FAT16

The FAT16 file system is widely used by DOS (DR-DOS, MS-DOS, PC-DOS, PTS-DOS and other), Windows 98/Me, and Windows NT/2000/XP operating systems and is supported by most other systems.

Main features of FAT16 are the file allocation table (FAT) and clusters. FAT is the core of the file system. To increase data safety, it is possible to have several copies of the FAT (there are usually two of them) on a single disc. A cluster is a minimum data storage unit in FAT16 file system. One cluster contains a fixed number of sectors. FAT stores information about what clusters are free, what clusters are bad, and also defines in which clusters files are stored.

The FAT16 file system has a 2GB limit that permits a maximum 65,507 clusters that are 32KB in size. (Windows NT/2000/XP support partitions up to 4GB with up to 64KB clusters). Usually the smallest cluster size is used to make the total cluster amount within the 65,507 range. The larger a partition is, the larger its clusters are. Usually the larger the cluster size, the more disc space is wasted. A single byte of datacould use up one cluster, whether the cluster size is 32KB or 64KB.

Like many other file systems, the FAT16 file system has a root folder. Unlike others,however, its root folder is stored in a special place and is limited in size (standard formatting produces a 512-item root folder).

Initially, FAT16 had limitations on file names. They could only be eight characters long, plus a dot, plus three characters of name extension. However, long-name support in Windows 95 and Windows NT bypassed this limitation. The OS/2 operating system also supports long names, but does so in a different way.


2)FAT32

The FAT32 file system was introduced in Windows 95 OSR2. It is also supported by Windows 98/Me/2000/XP. FAT32 is an evolved version of FAT16. Its main differences from FAT16 are 28-bit cluster numbers and a more flexible root, whose size is unlimited. The reasons FAT32 appeared are the support of large hard discs (over 8GB in capacity) and the impossibility of implementing any more complex file system into MS-DOS, which is still the basis for Windows 98/Me.

The maximum FAT32 disc size is 2 terabytes (1 terabyte, or TB, is equal to 1024 gigabytes, or GB).


3) NTFS

NTFS is the main file system for Windows NT/2000/XP. Its structure is closed, so no other operating system is fully supported. The main structure of NTFS is the MFT (master file table). NTFS stores a copy of the critical part of the MFT to reduce the possibility of data damage and loss. All other NTFS data structures are special files. NTFS stands for NT File System.

Like FAT, NTFS uses clusters to store files, but cluster size does not depend on partition size. NTFS is a 64-bit file system. It uses unicode to store file names. It is also a journaling (failure-protected) file system, and supports compression and encryption.

Files in folders are indexed to speed up file search.

[James Afflek]

Points to Remember


Compatibility

Before you decide what type of file system to use on a partition, you should consider compatibility. If multiple operating systems will access the partition, you must use a file system that all operating systems can read. Usually, this means using FAT because of its universal compatibility. Only Windows NT supports NTFS partitions.

Keep in mind, however, that this limitation only applies to the local machine. For example, if you have Windows NT and Windows 98 loaded on the same machine and both operating systems require access to a common partition, you must format that partition as FAT. However, if Windows NT is the only operating system on the PC, you can format the partition as NTFS, even if computers running other operating systems will access the partition across the network.


Volume Size

Another determining factor in your decision is the physical size of your partition. FAT only supports partition sizes up to 2 GB. If your partition size is larger than 2 GB, you must format it as FAT32 or NTFS, or you must break it into smaller partitions. You should also keep in mind that because of the enhanced features associated with NTFS, NTFS has more overhead than FAT. If your partition size is smaller than 200 MB, you should use FAT to avoid losing a large amount of disk space to the overhead associated with NTFS. The maximum size of an NTFS partition is 16 exabytes.


Fault Tolerance

Once you've considered your partition size and compatibility issues, you've got some flexibility in determining which file system is right for you. One issue to consider when making this decision is fault tolerance. Windows NT offers software support for several alternate disk access methods that increase speed and/or fault tolerance. These options include things such as disk striping and disk striping with parity. Many of these options require NTFS. If you're planning on using a hardware-based stripe set, you can use either file system.

Even without these advanced fault-tolerant options, NTFS includes built-in fault-tolerant capabilities well beyond the capabilities of FAT or FAT32. For example, when NTFS writes a change to the hard disk, it makes a record of the change in a log file. In the event of a power failure or a disk error, Windows NT can use these log files to repair your data.

NTFS also repairs hard disk errors automatically without displaying an error message. When Windows NT writes a file to an NTFS partition, it keeps a copy of the file in memory. It then reads back the file to make sure it matches the copy stored in memory. If the copies don't match, Windows NT marks that section of the hard disk as bad and won't try to use it again. It then uses the copy of the file stored in memory to rewrite the file to an alternate location on the hard disk.

The FAT and FAT32 file systems don't offer any of these safety features. While FAT and FAT32 do maintain two different copies of the file allocation table in case one copy is damaged, these systems are incapable of automatically fixing errors. Instead, you must run a utility such as ScanDisk.


Security

As I mentioned before, NTFS has its own built-in security system. You can grant various permissions to directories and to individual files. These permissions protect files and directories locally and remotely. For example, if someone were to try to access the restricted files, NTFS would protect those files.

If you're using FAT or FAT32, you depend on share permissions for security. Share permissions will protect a file across the network, but they offer no local protection. A person trying to access restricted files could simply sit at the local PC and gain full access to these files. Another disadvantage to share permissions is that they can be messy to manage. If you have hundreds of users on a server, each with his or her own directories, you could potentially end up with hundreds of shares, some of which may overlap, thus creating additional complications.


File Compression

Another advantage to NTFS is native support for file compression. If you ever used the compression program that came with MS-DOS 6.22, you may be groaning right now. As you may recall, the MS-DOS compression utility required you to compress your entire partition. The compression process took a long time and, when completed, drastically slowed your PC's file access. Another disadvantage was that a minor disk problem could potentially trash the entire partition. FAT32, on the other hand, offers no compression capabilities at all.

The NTFS compression is much better than its predecessors. It offers you the chance to compress individual files and directories of your choice. Because it compresses individual files, if you have a minor hard disk problem, it won't screw up your compression scheme and make you lose everything. Another advantage to compressing individual files and directories is that you can compress only seldom-used files. By doing so, you won't slow down your operating system by making it decompress files each time it needs to access them.


The System Partition

After reading this article, you may have decided that NTFS is far superior to FAT and FAT32. In most cases, if you're using Windows NT, you should use NTFS. However, this isn't always the case.

As I mentioned, NTFS partitions are only accessible via Windows NT. If you have a fatal error with Windows NT, you can't simply boot a system disk to a command prompt and fix a problem on an NTFS partition. To get around this problem, Microsoft recommends installing a second copy of Windows NT on your hard disk and using this copy to repair problems that occur on NTFS partitions.

Unfortunately, this method has some serious drawbacks. For starters, a second copy of Windows NT could consume up to 150 MB depending on which options you choose to load. Second, during the boot process, both copies share common files. Therefore, if your system partition (the partition your PC boots from) is formatted as NTFS and has a problem, you may not be able to boot either copy of Windows NT to fix the problem. While you may think the odds of a system partition error may be slim, just remember that many of the changes you may make to your disk partitions result in having to manually update the Boot.ini file. If you incorrectly update this file, Windows NT will become unbootable. Because this is an initial boot file on the system partition, every installed copy of Windows NT would share this file.

A better solution is to format your system partition as FAT. If you're concerned about security, simply make the system partition small and don't place anything other than the Windows NT system files on it. Remember that a FAT partition is safe from a security standpoint, as long as no unauthorized person has physical access to the machine.

[James Afflek]

Converting between File Systems

Converting to NTFS

If you're running Windows NT and want to use NTFS on some of your partitions that already contain data, you can easily convert a partition to NTFS. To do so, open an MS-DOS prompt window and type the following command:

CONVERT drive: /FS:NTFS

For example, if you wanted to convert your D drive to NTFS, you'd replace the word drive with the letter D, as shown below:

CONVERT D: /FS:NTFS

Converting to FAT32

Converting to FAT32 is even easier than converting to NTFS. To convert a FAT partition to FAT32 (within Windows 98), simply click Start and go to Program Files, Accessories, System Tools, Drive Converter (FAT32). When you do, you'll see a wizard that will allow you to select the partition you wish to convert and begin the conversion process. Before you convert a partition, however, remember that on older systems or systems with very full drives, this process can take several hours.