File Systems Technologies

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In this overview

A file system is a part of the operating system on a volume and it determines how files are named, stored, and organized on basic or dynamic disks. A file system manages files and folders as well as the information required to locate and access these items by local and remote users. The Microsoft Windows Server 2003 operating system supports the NTFS and FAT file systems.

When you format a volume on a hard disk, a file system is always required to access and manage data. You can put only one file system on a volume. If you partition your hard disk into multiple volumes, each volume can have a different file system.

All file systems used by Windows Server 2003 organize hard disks based on cluster size, which is determined by the number of sectors contained by the cluster. When a file is written to disk, the file system tries to find enough contiguous clusters to hold the file. If the file system cannot find contiguous clusters, it saves the file to noncontiguous clusters. The result is file fragmentation. Disk Defragmenter is a file system tool that organizes the clusters on the volume to be more contiguous, which, in turn, improves file system performance.

File Systems Components

NTFS is the preferred file system for Windows Server 2003. NTFS addresses many of the limitations of FAT file system-based file systems. It provides improved file security, as well as performance, reliability, and advanced features not found in any version of FAT. Use NTFS wherever possible to gain the maximum benefits from Windows Server 2003.

Although NTFS is the preferred file system for hard disks, Windows Server 2003 uses FAT12 for formatting floppy disks and FAT32 for formatting flash media and DVD-RAM discs.


The two versions of FAT supported by Windows Server 2003 are FAT16 and FAT32. FAT16 is an older file system. It was widely used on Windows NT 4.0, and supports a 16-bit file allocation table. FAT16 provides optimal performance on volumes that are less than 2 gigabytes (GB). FAT32 is the version of FAT introduced with Windows 95 OEM Service Release 2 (OSR2) and Windows 98. FAT32 supports a 32-bit allocation table, and supports smaller cluster sizes than FAT16, in order to more efficiently allocate space. On Windows Server 2003, FAT32 can support volumes up to 32 GB. FAT is also the only file system supported for floppy disks and other removable media.

Some earlier Microsoft Windows operating systems as well as removable disks and floppy disks support only the FAT file system. FAT16 and FAT32 volumes are limited to 4 gigabytes (GB) and 32 GB respectively, so you must use NTFS to create volumes larger than 32 GB.

Disk Defragmenter

Disk Defragmenter is a tool that is used to improve the overall performance of disk input or output on either NTFS or FAT-formatted volumes. Disk Defragmenter analyzes local volumes and consolidates fragmented files and folders so that each occupies a single, contiguous space on the volume. As a result, a system can access files and folders and save new ones more efficiently. By consolidating files and folders, Disk Defragmenter also consolidates a volume’s free space, making it less likely that new files will be fragmented.

File Systems Scenarios

This section describes a few scenarios in which NTFS, FAT, and Disk Defragmenter are used. Before formatting a volume for a file system, you should determine what the volume will be used for, and which operating system will be mounted on that volume. The following scenarios might help you when you are deciding how to format volumes.

NTFS Scenarios

This section describes scenarios in which NTFS should be the file system on a volume.

Increasing reliability

When a computer is restarted after a system failure, NTFS uses its log file and checkpoint information to restore the file system. In the event of a bad-sector error, NTFS dynamically remaps the cluster containing the bad sector and allocates a new cluster for the data. It also marks the cluster as bad so that it is no longer used. By formatting a POP3 mail server with NTFS, the mail store can offer logging and recovery. In the event of a server failure, NTFS can recover data by using its log files.

Increasing security

NTFS allows you to set permissions on a file or folder. You can also specify the groups and users who can access the file or folder, and set specific levels of access (for example, some users can only open the file, while other users can open it and modify it). NTFS also supports Encrypting File System (EFS) technology. Unauthorized users are prevented from accessing encrypted files, even if the unauthorized user has physical access to the computer. If a POP3 mail server is formatted with NTFS, NTFS provides increased security for the mail store (security that is not available with the FAT file system).

Supporting large volumes

Clusters are the smallest amount of disk space used to store a file. When you format a volume as NTFS, you can choose the cluster size of the volume. The smaller the cluster size, the more efficiently a disk stores information. You can create an NTFS volume which is up to 16 terabytes in size using the default cluster size (4 kilobytes (KB)) for large volumes, or you can create NTFS volumes of up to 256 terabytes using the maximum cluster size of 64 KB. NTFS also supports larger files and more files per volume than FAT. In addition, NTFS manages disk space more efficiently than FAT by using smaller cluster sizes. Using smaller clusters reduces wasted space on hard disks. NTFS supports the many capabilities of dynamic disks for managing large storage requirements.

Limited space on a volume

If your organization has limited space on a volume, NTFS provides support for increasing storage on a server with limited disk space.

Using features available only in NTFS

NTFS has a number of features that are not available if you are using a FAT file system. These include:

Using Windows Server 2003 features that require NTFS

Windows Server 2003 includes a number of features that require NTFS. A few of these features include:

In addition, NTFS is required before you can promote a server running Windows Server 2003 to a domain controller that hosts the Active Directory directory service.

FAT Scenarios

This section describes scenarios in which FAT should be the file system on a volume.

Mounting a server with a small volume

Small partitions (less than 512 megabytes) on a server work better with FAT. It uses a small amount of space on the partition, but still performs well.

Running multiple operating systems

If you are running multiple operating systems (for example, you are running Windows 98 in addition to Windows Server 2003), you must use FAT16 or FAT32 as Windows 98 is only supported by the FAT file system.

Using FAT with older operating systems

Both Windows 95 and Windows 98 use the FAT file system. These operating systems do not support NTFS.

Using FAT with removable disks

You must use FAT16 or FAT32 when formatting removable disks (for example, floppy disks). It is not possible to format a floppy disk with the NTFS file system because the file system itself requires too much disk space.

Disk Defragmenter Scenarios

This section describes scenarios in which Disk Defragmenter should be run on a volume.

Installing new software

Running Disk Defragmenter on a volume after installing software organizes the clusters on the volume.

Rewriting, updating and deleting files

Running Disk Defragmenter on a regular basis consolidates space to create more contiguous free clusters on the volume, which allows disk heads to read files and write updates more quickly.