Simulation Of DIsk Scheduling Algorithms

Abstract

Speed, accuracy and bulk storage are the essence of a computer system. One of the tasks of the operating system is the optimum utilization of available hardware. Operating System designers have always strived for achieving highest standards of speed, accuracy and efficient handling of secondary storage devices. Disk drives are the major secondary storage Input / Output device on all computers. Requests for disk input / output are generated by the file system and by the virtual memory system. Each request specifies the address on the disk to be referenced, in the form of a logical block number. In multiprogramming environment more processes need to access the disk for reading and writing of data at the same time. Therefore a queue of requests to be serviced, is always pending. It requires disk drives to have a fast access time and more bandwidth. We can improve both the access time and the bandwidth by scheduling the servicing of disk input / output requests in a better order. Different scheduling algorithms available for this purpose are First Come First Serve (FCFS), Shortest Seek Time First (SSTF), LOOK, C- LOOK, SCAN and CSCAN Scheduling. This work is to design and develop a simulator for disk scheduling utilizing SCAN (both up ward and down ward direction), C-SCAN algorithms and provide performance results. Simulation results will be compared with the previous [1] experimental results (obtained through FCFS, SSTF, LOOK and C-LOOK) to ascertain its efficacy and usefulness.