On a disk with 1000 cylinders 0 to 999 find the number of tracks the disk arm…
2012
On a disk with 1000 cylinders 0 to 999 find the number of tracks the disk arm must move to satisfy all the requests in the disk queue. Assume the last request service was at track 345 and the head is moving toward track 0. The queue in FIFO order contains requests for the following tracks 123, 874, 692, 475, 105, 376
- A.
2013
- B.
1219
- C.
1967
- D.
1507
Attempted by 51 students.
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Correct answer: B
The disk uses the SCAN algorithm moving towards track 0 first. The arm travels from 345 to 0, covering 345 tracks.
It then reverses direction and travels to the furthest request at track 874, covering 874 tracks. Total movement is 345 plus 874 equals 1219 tracks.
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