Consider a disk queue with requests for I/O blocks on cylinders: 98, 183, 37,…
2024
Consider a disk queue with requests for I/O blocks on cylinders: 98, 183, 37, 122, 14, 124, 65, 67 Considering FCFS (First Come First Served) scheduling, the total number of head movements is, if the disk head is initially at 53?
- A.
640
- B.
620
- C.
630
- D.
More than one of the above
- E.
None of the above
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Correct answer: A
Step 1: Start from initial head position 53. Step 2: Move to 98 (|98 - 53| = 45). Step 3: Move to 183 (|183 - 98| = 85). Step 4: Move to 37 (|37 - 183| = 146). Step 5: Move to 122 (|122 - 37| = 85). Step 6: Move to 14 (|14 - 122| = 108). Step 7: Move to 124 (|124 - 14| = 110). Step 8: Move to 65 (|65 - 124| = 59). Step 9: Move to 67 (|67 - 65| = 2). Total head movements = 45 + 85 + 146 + 85 + 108 + 110 + 59 + 2 = 640.