Microsoft® Windows Server™ 2003 Inside Out

Defragmenting Disks

As files are created, modified, and moved, fragmentation can occur both within the volume's allocation table and on the volume itself. This happens because files are written to clusters on disk as they are used. The file system uses the first clusters available when writing new data, so as you modify files, different parts of files can end up in different areas of the disk. If you delete a file, an area of the disk is made available, but it might not be big enough to store the next file that is created and as a result, part of a new file might get written to this newly freed area and part of it might get written somewhere else on the disk.

Although the file system doesn't care if the file data is on contiguous clusters or spread ...