NTFS vs. FAT

ONE GREAT STRENGTH OF WINDOWS NT is its ability to support multiple file systems. This ability stems from NT's modular approach to file system support. To support each file system, NT uses a low-level driver that's part of the Windows NT Executive. So creating support for additional file systems is as easy as developing and installing a new driver. (The sidebar, "Windows NT File Systems," on page 96, shows the file systems available under NT and provides a general description of each.)

An important decision in setting up an NT system is choosing a primary file system. With NT 3.5x, you had a choice of three file systems: NT File System (NTFS), File Allocation Table (FAT), and the OS/2 High-Performance File System (HPFS). In addition to support for the NTFS and FAT file systems, NT supports the CD-ROM File System (CDFS) for accessing data on PC-compatible CD-ROMs. NT 4.0 supports NTFS and FAT (to see how to make HPFS work with NT 4.0, see the sidebar, "Using HPFS with NT 4.0," page 98).

To decide what's right for your situation, you need to understand NTFS's and FAT's capabilities, advantages, and disadvantages. The sidebar, "Choosing an NT File System," on page 100, presents the pluses and minuses of both file systems. Let's start this look at file systems by clarifying some disk-related concepts and terms.

Disky Business
Every disk can contain partitions, or structural divisions. The two types of drive partitions are primary and extended. A primary partition is the only type that can contain an OS. You can assign a drive letter to each of up to four primary partitions on one physical drive. An extended partition is a special type of partition that you can subdivide into one or more logical drives. Each logical drive can have its own drive letter. You can have only one extended partition per physical drive, but the extended partition can have multiple logical drives (the number of logical drives on an extended partition has no practical limit). Each primary partition and each logical drive is formatted independently and can use a different file system.

A volume is a primary partition or logical drive that you format with a file system. In fact, any medium you can format, including a removable disk such as a floppy or CD-ROM, can be a volume.

System and Boot Partitions
NT gives special names to particular disk partitions. For example, the system partition contains hardware-specific files for booting the system. These files include the NT Boot Manager and boot.ini, ntdetect.com, and ntldr (osloader on RISC-based systems). The system partition can contain the NT installation directory.

On Intel x86-based computers, you can format the system partition with FAT or NTFS. On RISC-based computers, you must format the system partition with FAT. FAT partitions don't have NTFS's security capabilities, so NT 4.0 includes a new feature to secure the FAT system partition on a RISC-based NT system. From the NT Disk Administrator's partition menu, choose Secure System Partition. The system asks you to confirm the request. Click OK, and reboot the system to activate security on the system partition. With this feature, only Administrators group members can access the FAT system partition.

Another NT disk partition is the boot partition. Despite its name, this partition isn't necessarily the drive the system boots from. Instead, it contains the NT installation directory you choose during NT setup. The term boot refers to the files required to start NT, not the computer. The boot partition can be the same as the system partition. On RISC and Intel NT systems, the boot partition can be on a FAT or NTFS partition.

For maximum system security, administrators of RISC-based systems will want to consider separate partitions for the boot partition and the system partition and consider securing the system partition with the Secure System Partition option. This approach puts the NT system files on an NTFS partition (for better security and protection from data corruption than with FAT) and prevents access to the NT system files if the system boots from a DOS floppy, unless you use NTFSDOS (a shareware utility that can access an NTFS drive)--for information on NTFSDOS, see Mark Russinovich and Bryce Cogswell, "NTFSDOS Poses Little Security Risk," and Joel Sloss, "That Depends on Your Definition of Secure," September 1996).

The FAT File System
FAT is the granddaddy of all PC file systems. Several flavors of FAT have emerged over time, but the core technology is largely unchanged.

Features
Experienced DOS users will recognize some distinguishing characteristics of the FAT file system. It uses the file allocation table (FAT's namesake) to track files and directories. The system stores this table near the beginning of the FAT volume. To prevent corruption, the system automatically maintains a second copy of the table on the disk and can access this copy if the primary table becomes corrupt. The table and the volume's root (main) directory must be in specific locations on the disk so the system can access files needed to boot from a FAT volume.

The table needs constant updating, which requires that the hard drive heads continually return to the beginning of the volume. As a result, FAT can cause a severe performance hit on large volumes­the larger the volume, the greater the performance penalty.

FAT stores files on a first-come, first-served basis: The system writes files to disk in the first available area. Over time, this method can result in heavy file fragmentation (files are in multiple, noncontiguous disk blocks) on FAT volumes and is another performance killer. To remedy this problem, you have to run a disk defragmentation program.

As of this writing, the only NT disk defragmentation tool is Executive Software's DISKEEPER for Windows NT. No one utility can work with all the NT versions and service packs, and DISKEEPER is no different. With NT 3.5x, fragmentation utilities had to be specific to a particular NT version or service pack. If you use such a utility on a different version or service pack level, you can corrupt data. NT 4.0 solves this problem by including a disk defragmentation API. You can expect to see several new NT defragmentation tools available in the near future.

Another disadvantage to FAT is that its directory structure has no formal organization, so FAT can't automatically sort folders and filenames in a directory. Locating a file on a large FAT volume can take longer than searching an NTFS volume with automatic directory sorting.