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GATE CS 2021 : Operating system 10

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Question 1

Consider a disk system with 100 cylinders. The requests to access the cylinders occur in following sequence:
4, 34, 10, 7, 19, 73, 2, 15, 6, 20
Assuming that the head is currently at cylinder 50, what is the time taken to satisfy all requests if it takes 1 ms to move from one cylinder to adjacent one and shortest seek time first policy is used ?

Question 2

Using a larger block size in a fixed block size file system leads to

Question 3

Consider an operating system capable of loading and executing a single sequential user process at a time. The disk head scheduling algorithm used is First Come First Served (FCFS). If FCFS is replaced by Shortest Seek Time First (SSTF), claimed by the vendor to give 50% better benchmark results, what is the expected improvement in the I/O performance of user programs?

Question 4

Which of the following is not the disk scheduling algorithm?

Question 5

Which of the following operation is performed by swap space?

Question 6

Disk requests are received by a disk of cylinders 5,25,18,3,39,8 and 35 in that order for seek take 5 millisecond per cylinder. How much seek time is needed to serve these requests for a shortest seek time first algorithm? Assume that the arm is at cylinder 20.

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