In computing, file system fragmentation, sometimes called file system aging, is the tendency of a file system to lay out the contents of files non-contiguously to allow in-place modification of their contents. It is a special case of data fragmentation. File system fragmentation increases disk head movement or seek time, which are known to hinder throughput. In addition, file systems cannot sustain unlimited fragmentation. The correction to existing fragmentation is to reorganize files and free space back into contiguous areas, a process called defragmentation.