Scheduling Models
Prior to beginning work on this assignment, read the following sections in your textbook: 9.1 to 9.6 and 9.9 in Chapter 9: Mass-Storage Structure. Finally, read the Operating System – Scheduling Algorithms tutorial.
Part 1:
To complete this assignment, consider the following scenario:
- A disk drive has 300 cylinders, numbered 0 to 299. The drive is currently serving a request at cylinder 51, and the previous request was at cylinder 56. The pending requests are received in the following order: 72, 56, 103, 111, 17, 189, 236, 198, and 88.
Describe how the disk arm moves to satisfy all the pending requests for each of the following disk-scheduling algorithms. (Perhaps you create a diagram similar to the diagrams in Section 9.4 to support your explanation.)
- FCFS
- SSTF
- SCAN
Calculate the total distance (in cylinders) that the disk arm moves for each of the above disk-scheduling algorithms. Compare the algorithms and explain which algorithm is the most efficient (the shortest distance) for this scenario. Write a minimum of 250 words.
Part 2:
Compare the algorithms and determine which is the fairest for the next process in the queue. Explain why this algorithm will always be the fairest disk-scheduling algorithm.
Describe an example of circumstances where fairness would be an important goal. Describe a scenario where it would be important that the operating system be unfair. Write a minimum of 250 words.
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