Consider a disk system with 100 cylinders. The request to access the cylinders…
2017
Consider a disk system with 100 cylinders. The request to access the cylinders occur in the following sequences 4, 37, 10, 7, 19, 73, 2, 15, 6, 20 Assuming 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 algorithm is used.
- A.
95 msec
- B.
119 msec
- C.
233 msec
- D.
276 msec
Attempted by 75 students.
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Correct answer: B
The Shortest Seek Time First (SSTF) algorithm selects the request closest to the current head position. Starting at cylinder 50, the sequence of visited cylinders is 37, 20, 19, 15, 10, 7, 6, 4, 2, and finally 73. Summing the absolute differences between consecutive positions yields a total seek distance of 119 cylinders. Since each movement takes 1 ms, the total time is 119 msec.
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