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ISRO CSE 2018 | Question: 23

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Disk requests come to a disk driver for cylinders in the order $10$, $22$, $20$, $2$, $40$, $6$ and $38$ at a time when the disk drive is reading from cylinder $20$. The seek time is $6$ ms/cylinder. The total seek time, if the disk arm scheduling algorithms is first-come-first-served is

  1. $360$
  2. $850$
  3. $900$
  4. None of the above

5 Answers

Best answer
10 10 votes

In FCFS, the request which comes first to disk driver is served first.

Given cylinder Queue: $10, 22, 20, 2, 40, 6, 38$

Head Movements:$(20-10)+(22-10)+(22-2)+(40-2)+(40-6)+(38-6)=146$
Seek Time= $6ms$/cylinder

For $146$ seeks, seek time= $6*146=876ms$ 

Hence Option d) is the correct answer

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2 2 votes

In FCFS, the request which comes first is served first.

Given cylinder Queue: $10, 22, 20, 2, 40, 6, 38$

Head Movements:$(20-10)+(22-10)+(22-2)+(40-2)+(40-6)+(38-6)=146$

Seek Time= $6ms$/cylinder

For $146$ seeks, seek time= $6*146=876ms$ 

Option d) is the correct answer

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