When file systems store a file, they usually try to store the whole file in one part. When the disk drive fills up, finding an empty space that is large enough becomes more difficult. In such a case, the file systems will split the file into parts, and store each part at a different location on the disk. This process is known as fragmentation. Fragmentation occurs because the different parts are not stored next to one another. When the file is read, it has to be assembled from the different locations. Files that are stored in one part can be read faster.