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Starting from the current head position, what is total distance (in Cylinders) that the disk arm moves to satisfy all the pending requests for each of the following disk scheduling algorithms?

Suppose that a disk drive has 5000 cylinders, numbered 0 t0 4999. The drive is currently servicing a request at cylinder 143 and the previous request was at cylinder 125. The queue of pending requests , in FIFO order 86, 1470 , 913, 1774, 948, 1509, 1022, 1750, 130.

Starting from the current head position, what is total distance (in Cylinders) that the disk arm moves to satisfy all the pending requests for each of the following disk scheduling algorithms?

(i) SCAN

(ii) C-Look


Subject: Operating System

Topic: STORAGE MANAGEMENT

Difficulty: Hard

1 Answer
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SCAN

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Total Distance traveled

= |143-913|+|913-948|+|948-1022|+|1022-1470|+|1470-1509|+|1509-1750|+|1750-1774|+|1774-4999|+|4999-180|+|180-86|

=9769

C-LOOK

enter image description here

Total distance traveled

= |143-913|+|913-948|+|948-1022|+|1022-1470|+|1470-1509|+|1509-1750|+|1750-1774|+|1774-86|+|86-130|

=3363

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