Performance evaluation of disk scheduling algorithms in the presence of bad sectors

Disk scheduling algorithms have long been a topic of study in computer science. Many researchers studied the performance of the disk scheduling algorithms. However, perhaps due to the difficulty of implementation, those early works focused solely on exploring the basic ideas and comparing the performance of these algorithms. No one studied the effect of bad sectors in their performance. In this paper, the performance of the disk scheduling algorithms in the presence of bad sectors is studied. The mapping of bad sectors to spare sectors is considered. We use simulation to do the performance evaluation. Simulation results show that all disk scheduling algorithms are same when there is a high percentage of bad sectors and when the spare sectors are distributed at the end of the disk. It is shown also that with a high percentage of bad sectors, the disk scheduling algorithms perform better if the distribution of spare sectors is at the end of the disk. With a low percentage of bad sectors, the scheduling algorithms perform better if the distribution of spare sectors is within the entire disk. It is shown also that all scheduling algorithms are more sensitive to bad sectors in heavily loaded systems.