hdd hard drive group data sector all file split fragment write sector hard drive note fragment write sector arbitrary orderone problem hdd hard drive follow magnetic head sector read filefind time need read file split n fragment the ith sector contain fith fragment file 1fin note different sector contain different fragment at start magnetic head position contain fragment the file reading follow manner fragment read magnetic head move sector contain second fragment second fragment read nth fragment read the fragment read order nthIt take ab time unit magnetic head sector sector b read fragment take time