Simulation of a two head disk scheduling algorithm: An algorithm determining the algorithm to be imposed on the heads based on the nature of track requests

To write data on a disk block or to read data from a disk block, three factors are considered: seek time, rotational delay and actual data transfer time. The seek time is the time taken to move the arm to the proper cylinder and the rotational delay is the time for the proper sector to rotate under the head. The seek time dominates the other two factors by a wide margin. Thus, disk scheduling algorithms are used to reduce the seek time and improve the performance of the system substantially. There exist several disk scheduling algorithms like FCFS (First Come First Serve), SSTF (Shortest seek time first), SCAN (for both directions), C-SCAN (Circular SCAN), LOOK (for both directions) and C-LOOK (Circular LOOk). All these algorithms use a single head. The proposed algorithm uses two heads instead of one thereby improving the performance of modern storage devices in terms of throughput. The throughput can be increased by reducing total head movements. The working of the proposed algorithm has 4 cases based on the nature of requested tracks. When both the heads are working together, they serve the requests of their areas and do not overlap. In some cases, only a single head is used to serve all the requests, thus improving the battery usage.