NTFS stands for NT File System, is an advanced, high-performance file system designed initially for use with the Microsoft Windows NT and Windows 2000 operating systems. NTFS is superior to the file allocation table (FAT) file system in many respects, providing better performance, reliability, and compatibility.
NTFS includes security features for data access control and ownership privileges that make it suitable for file servers, Web servers, and application servers in the corporate networking environment.
The following table shows a comparison between the features of NTFS and FAT.
NTFS compared with FAT
| Feature | NTFS | FAT |
| Local security | x | |
| File-level access permissions | x | |
| Automatic recoverability using lazy writes and transaction logging | x | Lazy writes only |
| File-level compression | x | |
| POSIX-compliant | x | |
| Supports Services for Macintosh | x | |
| Dual boot with Windows 95 and Windows 98 | x | |
| Maximum volume size | 232 = 4 GB | 264 = 32 EB (theoretical)241 = 2 TB (practical) |
| Optimal volume size | Less efficient for volumes over ~500 MB | Less efficient for volumes under ~50 MB |
How It Works
Like FAT, NTFS uses the cluster as the fundamental unit of disk space allocation. The default size of the clusters for an NTFS volume depends on the size of the volume, as shown in the table. When you create a new NTFS volume by formatting a disk partition with NTFS, the master file table (MFT), which contains information concerning all the files and folders stored on the volume, is created.
The MFT is located on the disk immediately after the partition boot sector, which contains the BIOS parameter block and the code that enables the operating system to find and load the startup files. After the MFT comes NTFS system files, which help implement NTFS by storing information such as the contents of the volume, volume name and version, table of attribute names and numbers, a list of transaction steps used for NTFS recoverability, the root folder, and so on.
After the NTFS system files is the file area where user data can be stored. The total overhead of the MFT and NTFS system files is about 1 MB.
Default Cluster Sizes for NTFS
| Volume Size | Sectors/Cluster | Cluster Size |
| 512 MB or less | 1 | 512 bytes |
| 513 KB–1024 MB | 2 | 1 KB |
| 1025 MB–2048 MB | 4 | 2 KB |
| 2049 MB–4096 MB | 8 | 4 KB |
| 4097 MB–8192 MB | 16 | 8 KB |
| 8193 MB–16384 MB | 32 | 16 KB |
| 16385 MB–32768 MB | 64 | 32 KB |
| 32769 MB or more | 128 | 64 KB |
NTFS on Windows 2000
NTFS on Windows 2000 includes additional features not supported by NTFS on Windows NT.
These features are used to provide greater manageability and enhanced security, and to support the new Active Directory of Windows 2000. They include the following:
- Multiple data streams: Allow libraries of files to be defined as alternate streams
- Reparse points: Alter the way NTFS resolves path names
- Change journal: Provides a persistent log of all changes made to files on the volume
- Encryption: Allows data to be stored in encrypted form
- Sparse file support: Allows programs to create very large files while consuming disk space only as needed
- Disk quotas: Allow administrators to control how much disk space users have access to
Note that Windows NT 4.0 systems must be running Service Pack 4 or later to read basic volumes formatted using the Windows 2000 version of NTFS. Also, because of the different disk structures, Windows NT 4 disk utilities such as autochk and chkdsk will not work on Windows 2000 NTFS volumes. Because of these incompatibilities, Microsoft does not recommend dual booting between Windows NT 4 and Windows 2000.
