Disk Defragmentation

What Does Disk Defragmentation Mean?

Defragmentation is the process of consolidating fragmented files on the user's hard drive. Files become fragmented when data is written to disk, and there is not enough contiguous space to hold the complete file. Storage algorithms break the data apart so that it will fit into the available space.


The process of defragmentation moves the data blocks on the hard drive around to bring all the parts of a file together. Defragmentation reduces file system fragmentation, increasing the efficiency of data retrieval and thereby improving the overall performance of the computer. At the same time, it cleans the storage and provides additional storage capacity.

Defragmentation is the opposite of fragmentation, which is an inefficient use of computer storage.

Techopedia Explains Disk Defragmentation

Fragmentation occurs gradually as users change, save, or delete files. The saved modifications for a file are usually stored at a hard drive location that is different from that of the original file. Supplementary modifications are stored to even more locations. Gradually, both the file and the hard drive become fragmented, and the computer becomes very slow as it needs to search in various places to open a file.

Windows-based computers require periodic defragmentation; Unix and Linux-based computers do not because of a different design for storing data, even if the same hardware is used. Microsoft Windows provides a proprietary defragmenting tool within its OS. Third-party versions also are available.

Back-end processes such as reading and writing storage media are always invisible to users, who are unable to continuously defragment storage devices because of the impact this has on a system's rhythm
Defragmentation tools were introduced to eliminate this issue and are preinstalled in different versions of the Windows OS. These built-in defragmenters rearrange the hard drive data and reunite the fragmented files, which helps the computer to run more efficiently. A hard drive uses automatic schedulers for periodic defragmentation. In addition, users may use tools for storage media defragmentation, such as:

  • Microsoft Windows 98: This OS contains a built-in defragmentation tool available via the system’s Tools menu.
  • Microsoft Windows NT: This OS was released without a defragmenter tool because its new technology file system (NTFS) was designed for automatic system defragmentation. However, third-party defragmentation tools are often used.
  • Microsoft Windows 2000: This OS is equipped with defragmentation tools, which are more efficient than those found in earlier Windows operating systems.
  • Microsoft Windows XP and Windows 7: These operating systems contain default disk defragmentation tools.

Techniques to reduce defragmentation include partitioning and optimization, which allow users to create logical OS hard drives. Programs such as Internet Explorer and databases should be partitioned separately to reduce potential storage media fragmentation.


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Margaret Rouse

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.