Disk Head Simulator Case Study

Using the Disk Head Simulator
Introduction
Secondary storage is a very significant component of a computer’s operating environment. It provides an important large storage space that can permanently hold systems software and any other desired user data. Secondary storage can also be utilized as a backup to ensure that the computer system is reliable and that data carried is safe. In addition, secondary storage also known as the Disk system supports the operations of the main memory. Therefore, we can say that the optimal performance of the disk is crucial since it affects the overall operation of the system (Silberschatz, Galvin and Gagne). To be able to read or write a sector of the disk, the disk arm needs to first and foremost search for
Several standard scheduling algorithms including Shortest Seek Time First (SSTF), First-Come/First-Served, Look, Scan, C-look, and C-Scan are supported by this application. Blocks that the algorithms are to seek are either generated on the go using distributions or are set up as a list in a file. In most cases the blocks can either all arrives at a later time or before the simulation begins (Using the Disk Head Simulator).
When carrying out this simulation, the seek time can be assumed as any linear function of the cylinders available. This Disk Head Simulator offers support to both a zoned block layout where the physical disks are subdivided into sections and a uniform layout of blocks, i.e. each cylinder having a fixed number of blocks. The Disk Head Simulator assumes that the scheduling is entirely being done by the OS (operating system). Normally, the simulator assumes that the OS has knowledge of how the disk is layered or the disk is able to use any layout. For instance, the OS can utilize the logical block addressing whereby it assumes that each cylinder is associated with a particular block and the disk has a zoned physical layout. Through the use of the Disk Head Simulator, we are able to explore this mismatch. Numerical and graphical analysis of these algorithms may be preferred for scheduling
It gives a clear comparison of the different algorithms that were run including FCFS, SSTF, and the C-LOOK.
Conclusion
The SSTF scheduling algorithm results in almost one-third more than the distance that FCFS scheduling algorithm would have taken if it was used for this queue. This implies that, compared to the FCFS algorithm, it offers a substantially improved performance. However, SSTF algorithm is not optimal and may at times cause starvation of some request which might have arrived earlier but are far away from the others and the current position of the disk head. Therefore, it can be concluded that the SSTF scheduling algorithm when compared to the FCFS algorithm reduces the total cylinder movement of the head but is not optimal just as the SJF