Consider a disk with tracks numbered 0 to 199. The current head position is 50 (Head Movement is Right). The request queue is: 98, 183, 37, 122, 14, 124, 65, 67. How Many Head movements are there in servicing requests using SSTF?Tip: Enter numerical data ONLY. E.g: "5" and NOT "5 Head Movements".

Question

BlackTom AI · Accepted Answer

We start by identifying the initial head position and the queue of requests to be serviced using SSTF (Shortest Seek Time First).

Initial head position: 50. Pending requests: 98, 183, 37, 122, 14, 124, 65, 67.

Step 1: From 50, compute distances to each request: |50-98|=48, |50-183|=133, |50-37|=13, |50-122|=72, |50-14|=36, |50-124|=74, |50-65|=15, |50-67|=17. The smallest distance is 13 to 37. Move to 37. Cumulative movements: 13. Remaining: 98, 183, 122, 14, 124, 65, 67.

Step 2: From 37, distances: to 98=61, to 183=146, to 122=85, to 14=23, to 124=87, to 65=28, to 67=30. Closest is 14 at distance 23. Move to 14. Cumulative: 13+23=36. Remaining: 98, 183, 122, 124, 65, 67.

Step 3: From 14, distances: to 98=84, to 183=169, to 122=108, to 124=110, to 65=51, to 67=53. Closest is 65 at distance 51. Move to 65. Cumulative: 36+51=87. Remaining: 98, 183, 122, 124, 67.

Step 4: From 65, distances: to 98=33, to 183=118, to 122=57, to 124=59, to 67=2. Closest is 67 at distance 2. Move to 67. Cumulative: 87+2=89. Remaining: 98, 183, 122, 124.

Step 5: From 67, distances: to 98=31, to 183=116, to 122=55, to 124=57. Closest is 98 at distance 31. Move to 98. Cumulative: 89+31=120. Remaining: 183, 122, 124.

Step 6: From 98, distances: to 183=85, to 122=24, to 124=26. Closest is 122 at distance 24. Move to 122. Cumulative: 120+24=144. Remaining: 183, 124.

Step 7: From 122, distances: to 183=61, to 124=2. Closest is 124 at distance 2. Move to 124. Cumulative: 144+2=146. Remaining: 183.

Step 8: From 124 to 183: distance 59. Move to 183. Cumulative: 146+59=205. All requests serviced.

Total head movements (SSTF): 205.

Consider a disk with tracks numbered 0 to 199. The current head position is 50 (Head Movement is Right). The request queue is: 98, 183, 37, 122, 14, 124, 65, 67. How Many Head movements are there in servicing requests using SSTF?Tip: Enter numerical data ONLY. E.g: "5" and NOT "5 Head Movements".

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Consider a disk with tracks numbered 0 to 199. The current head position is 50 (Head Movement is Right). The request queue is: 98, 183, 37, 122, 14, 124, 65, 67. How Many Head movements are there in servicing requests using SSTF?Tip: Enter numerical data ONLY. E.g: "5" and NOT "5 Head Movements".

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