NTFS file system

Definition of NTFS file system in The Network Encyclopedia.

What is NTFS file system?

An advanced, high-performance file system designed 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.

Graphic N-5. Structure of an NTFS volume.

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

NOTE

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.

TIP

Here are some recommendations for installing Windows NT Server on a system:

  • Partition your hard disk into at least two volumes, or use two or more separate hard drives.
  • Your C volume, which contains the operating system, should be 250 to 500 MB in size and formatted with FAT. This gives you a back door for replacing missing or corrupt system files by using an MS-DOS boot disk. If you change your mind later and want to better secure C using NTFS, you can convert a FAT volume to NTFS by using the convert command.
  • Your other volumes, which contain your application files and data files, should be formatted in NTFS. This gives the files the greater protection that NTFS provides and offers you greater control over access to data shared over the network.

For installing Windows 2000 Server on a system, Microsoft recommends using NTFS for the C partition. You should have a minimum of 1.2 GB of free space on this partition, but at least 2 GB free is recommended.