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What Is Disk Defragmenter?

Updated: March 28, 2003

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

What Is Disk Defragmenter?

In this section

When you create, copy, or move a file on your hard disk, the operating system looks for blocks of contiguous free disk space where it can write the file. When the operating system cannot find enough contiguous space, it looks for free space scattered throughout the hard disk to which the file can be written in pieces. As a result, pieces of the file may end up scattered over the hard disk rather than in one contiguous chunk. When a file is written to non-contiguous free space, it is known as a fragmented file.

All Windows file systems are susceptible to fragmentation, regardless of the type of file system or the type of disk. When a volume contains many fragmented files and folders, it requires several additional disk drive reads and more movement of the disk drive heads to collect the various pieces, resulting in Windows taking much longer to read a file. Similarly, creating new files and folders also takes longer when the free space available on the volume is scattered. If the free space is not consolidated, then subsequent files written to the volume will more likely be fragmented.

Disk Defragmenter is both a Microsoft Management Console (MMC) snap-in and a command-line utility that can be used to optimize NTFS- or FAT-formatted volumes. Disk Defragmenter rearranges files so that files and free space are consolidated. A reduction in fragmentation results in a reduction in the amount of mechanical movement required to locate all clusters of a file.

Common Scenarios for Disk Defragmenter

Disk Defragmenter is commonly used in the following scenarios.

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.

Disk Defragmenter Interactions

Disk Defragmenter interacts with the following technologies.

NTFS and FAT file systems

You can use Disk Defragmenter to reduce fragmentation and improve the overall performance of disk input and output (disk I/O) on either NTFS- or FAT-formatted volumes by performing online defragmentation of the master file table (MFT) on NTFS volumes or by working on volumes with any cluster size.

Related Information

The following resources contain additional information that is relevant to this section.

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