When files are saved to a hard disk, they aren’t necessarily saved in an area of contiguous disk space. For example, a 10 K file might be fragmented and spread over three disparate disk clusters, each 4 K in size. When this file is accessed, the system needs to obtain the contents of each of the clusters to open it, which would involve reading different areas of the disk for a single file. When defragmentation is performed, fragments of the same file are saved in contiguous areas of disk space, thus speeding up read access to the file and improving performance.
