c) Suppose a disk has 300 cylinders, numbered from 0 to 299. The drive is currently serving an I/O request at cylinder 111 and the disk head was previously serving a request at cylinder 99, and there is a queue of disk access requests for cylinders as below: 181, 199, 150, 160, 85, 178, 109, 75 Starting from the current head position, calculate the total head movements using the following disk scheduling algorithms. (i) SSTF scheduling (ii) SCAN scheduling

c) Suppose a disk has 300 cylinders, numbered from 0 to 299. The drive is currently serving an I/O request at cylinder 111 and the disk head was previously serving a request at cylinder 99, and there is a queue of disk access requests for cylinders as below: 181, 199, 150, 160, 85, 178, 109, 75 Starting from the current head position, calculate the total head movements using the following disk scheduling algorithms. (i) SSTF scheduling (ii) SCAN scheduling

Operations Research : Applications and Algorithms

4th Edition

ISBN:9780534380588

Author:Wayne L. Winston

Publisher:Wayne L. Winston

Chapter20: Queuing Theory

Section20.10: Exponential Queues In Series And Open Queuing Networks

Problem 11P

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8. Consider one disk with 400 cylinders, numbered 0 to 399. Assume the current position of head is at cylinder 130. The request queue is given as follows: 150, 40, 350, 100, 280 For each of the disk-scheduling algorithms given below, show (by plotting in the graphs below) the current position of head based on the disk arm movement to satisfy the above requests, and count the total distance (in cylinders) of the disk arm movement. a. First Come First Served (FCFS) 0 40 100 1.30 150 Total distance (disk am movement) = b. Shortest Seek Time First (SSTF) 40 100 130 150 0 Total distance (disk arm movement) = c. LOOK - in the direction of increasing track number 0 40 100 130 150 Total distance (disk arm movement) = 280 280 280 350 350 350 399 399 399
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