[2021] PSU - CMPSC 473 Operating Systems - Final Exam - Q7 Disk Scheduling
Q7
Consider a magnetic disk drive consisting of 200 tracks numbered 0, ..., 199whose scheduler employs the Elevator (SCAN) algorithm. Consider a set of 10requests that arrive at the same time to this drive's scheduler. We will denote each request by the track number on which its requested disk block resides. Assume the disk head to be on track 33 and the last request it serviced to have been on track 22. Calculate the average number of tracks that the disk head needs to traverse to service these 10 requests. Hint: remember that, in SCAN, the disk arm moves all the way to the last track in its current direction before changing direction.
132, 92, 30, 14, 45, 7, 8, 9, 133, 99.
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