Question

why is disk fragmentor useful

Answer 1

Disk defragmentation divides the hard disk into different parts called fragments which are rather easier to be searched for errors than the whole disk. It also makes the process faster.

Answer 2

Defrag" is short for "defragment," which is a maintenance task required by your hard drives. Most hard drives have spinning platters, with data stored in different places around that platter. ... The hard drive then takes longer to read that file because the read head has to "visit" multiple spots on the platter...............