Disk-drive with efficient command-reordering

A storage device includes a disk, a head configured to write data to and read data from the disk, and a controller. The controller is configured to, for each of a plurality of unexecuted commands, carry out a calculation of an amount of time that is required for the head to start accessing the disk to begin execution of the non-executed command upon completion of a currently-executed command, until the earlier of i) a number of unexecuted commands for which the calculation has been carried out reaches a threshold value or ii) the completion of the currently-executed command, select a next command to be executed from one or more unexecuted commands for which the calculation has been carried out, based on the calculated amount of time for each of the one or more unexecuted commands, and execute the selected next command.