Question

I need a full solution to this question. ( Operating Systems )

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Suppose that a disk has 5000 cylinders, numbered 0 to 1999. The drive is currently serving a request at cylinder 143, and the previous request was at cylinder 152. The queue of pending requests is as follows: 130, 1750 1022, 1509, 948, 1774, 913, 1470, 86 Starting from the current head position, what is total "seek time" for the following disk scheduling algorithms? 1. FCFS 2. SSTF 3. LOOK 4. C-Scan FCFS 0 86 125 130 143 913 948 1022 1470 1509 1750 1774 1999

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thank you.

Answer 1

FCFS 0 86 125 130 143_913 948 1022 1470 15091750 1774 1999 1620 728 487 561 820- 861 557 1384 total = 7037

SSTF 0 130 913 948 1022 1470 15091750 1774 1999 86 | 125 44 143 13 left total = 143-86 = 57 Right total = 1774-86 =1688 total = 1745

LOOK 0 86 125 130 143 913 948 1022 1470 1509 1750 1774 1999 left total = 143-86 = 57 Right total = 1774-86 =1688 total = 1745

C-SCAN 0 86 125 130 143 913 948 1022 1470 15091750 1774 1999 143 1999 1086 total = 143 + 1999 + 1086 = 3228