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On a disk with 1000 cylinders, number 0-999. compute the number off tracks the disk arm must move to satisfy all request in the disk queue.

Assume the latest request received was at track 345 and the head is moving towards track 0. the queue in FIFO order contains request for the following tracks. 123,874,692,475,105,376. Perform the computation for the following scheduling algorithms. i)FIFO ii)SSTF iii)SCAN

Subject: Operating System

Topic: STORAGE MANAGEMENT

Difficulty: Hard

1 Answer
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FIFO

The FIFO schedule is 345,123,874,692,475,105 and 376.

Total head movement = (345-123) + (874-123) + (874-692) + (692-475) + (475-105) + (376-105) =2013

SSTF

The SSTF schedule is 345,376,475,692,874,123 and 105.

Total head movement = (376-345) + (475-376) + (692-475) + (847-692) + (874-123) +(123-105) = 1298

SCAN

The SCAN schedule is 345,123,105,0,376,475,692 and 874.

Total head movement = (345-123) + (123-105) + (105-0) + (0-376) + (376-475) +(475-692) + (692-874) = 1219

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