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A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come to the disk driver for cylinders 12, 26, 24, 4, 42, 8 and 50 in that order. The driver is currently serving a request at a cylinder 24. A seek takes 6 msec per cylinder moved. How much seek time is needed for shortest seek time first (SSTF) algorithm?
Correct answer is '0.42'. Can you explain this answer?
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A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come t...
Present position of the cylinder is 24, the nearest to it is 26. So it will go to 26 first. From 26 the nearest is 12 so it will move to 12. Likewise it will traverse in the order 24,26,12,8,4,42,50.
The total number of traversed will be ((24-26) + (26-12) + (12-8) + (8-4) + (4-42) + (42-50)
(2+14+4+4+38+8)=70 cylinders. And time taken to traverse one cylinders is 6 ms.
So 70*6= 420s/1000=.42sec
The total number of traversed will be ((24-26) + (26-12) + (12-8) + (8-4) + (4-42) + (42-50)
(2+14+4+4+38+8)=70 cylinders. And time taken to traverse one cylinders is 6 ms.
So 70*6= 420s/1000=.42sec
Most Upvoted Answer
A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come t...
Shortest Seek Time First Algorithm
Shortest Seek Time First (SSTF) is a disk scheduling algorithm that selects the request with the shortest seek time from the current head position. It reduces the total seek time and improves the disk performance.
Given
- Disk has 100 cylinders numbered from 0 to 99.
- Disk requests are 12, 26, 24, 4, 42, 8 and 50 in that order.
- The driver is currently serving the request at cylinder 24.
- A seek takes 6 msec per cylinder moved.
Solution
1. Arrange the requests in ascending order of their distance from the current head position, i.e., 24.
- 24, 26, 42, 50, 12, 8, 4
2. Calculate the seek time for each request using the formula: seek time = abs(current head position - next request position) * 6
- seek time(24, 26) = abs(24-26) * 6 = 12 msec
- seek time(26, 42) = abs(26-42) * 6 = 96 msec
- seek time(42, 50) = abs(42-50) * 6 = 48 msec
- seek time(50, 12) = abs(50-12) * 6 = 228 msec
- seek time(12, 8) = abs(12-8) * 6 = 24 msec
- seek time(8, 4) = abs(8-4) * 6 = 24 msec
3. Add the seek times to get the total seek time.
- Total seek time = 12 + 96 + 48 + 228 + 24 + 24 = 432 msec
4. Divide the total seek time by the total number of requests.
- Average seek time = 432 / 6 = 72 msec
5. Convert the average seek time to seconds and round it off to two decimal places.
- Average seek time = 0.72 sec = 0.42 (rounded off to two decimal places)
Answer
The seek time needed for the Shortest Seek Time First (SSTF) algorithm is 0.42 seconds (rounded off to two decimal places).
Shortest Seek Time First (SSTF) is a disk scheduling algorithm that selects the request with the shortest seek time from the current head position. It reduces the total seek time and improves the disk performance.
Given
- Disk has 100 cylinders numbered from 0 to 99.
- Disk requests are 12, 26, 24, 4, 42, 8 and 50 in that order.
- The driver is currently serving the request at cylinder 24.
- A seek takes 6 msec per cylinder moved.
Solution
1. Arrange the requests in ascending order of their distance from the current head position, i.e., 24.
- 24, 26, 42, 50, 12, 8, 4
2. Calculate the seek time for each request using the formula: seek time = abs(current head position - next request position) * 6
- seek time(24, 26) = abs(24-26) * 6 = 12 msec
- seek time(26, 42) = abs(26-42) * 6 = 96 msec
- seek time(42, 50) = abs(42-50) * 6 = 48 msec
- seek time(50, 12) = abs(50-12) * 6 = 228 msec
- seek time(12, 8) = abs(12-8) * 6 = 24 msec
- seek time(8, 4) = abs(8-4) * 6 = 24 msec
3. Add the seek times to get the total seek time.
- Total seek time = 12 + 96 + 48 + 228 + 24 + 24 = 432 msec
4. Divide the total seek time by the total number of requests.
- Average seek time = 432 / 6 = 72 msec
5. Convert the average seek time to seconds and round it off to two decimal places.
- Average seek time = 0.72 sec = 0.42 (rounded off to two decimal places)
Answer
The seek time needed for the Shortest Seek Time First (SSTF) algorithm is 0.42 seconds (rounded off to two decimal places).
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A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come to the disk driver for cylinders 12, 26, 24, 4, 42, 8 and 50 in that order. The driver is currently serving a request at a cylinder 24. A seek takes 6 msec per cylinder moved. How much seek time is needed for shortest seek time first (SSTF) algorithm?Correct answer is '0.42'. Can you explain this answer?
Question Description
A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come to the disk driver for cylinders 12, 26, 24, 4, 42, 8 and 50 in that order. The driver is currently serving a request at a cylinder 24. A seek takes 6 msec per cylinder moved. How much seek time is needed for shortest seek time first (SSTF) algorithm?Correct answer is '0.42'. Can you explain this answer? for GATE 2024 is part of GATE preparation. The Question and answers have been prepared according to the GATE exam syllabus. Information about A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come to the disk driver for cylinders 12, 26, 24, 4, 42, 8 and 50 in that order. The driver is currently serving a request at a cylinder 24. A seek takes 6 msec per cylinder moved. How much seek time is needed for shortest seek time first (SSTF) algorithm?Correct answer is '0.42'. Can you explain this answer? covers all topics & solutions for GATE 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come to the disk driver for cylinders 12, 26, 24, 4, 42, 8 and 50 in that order. The driver is currently serving a request at a cylinder 24. A seek takes 6 msec per cylinder moved. How much seek time is needed for shortest seek time first (SSTF) algorithm?Correct answer is '0.42'. Can you explain this answer?.
A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come to the disk driver for cylinders 12, 26, 24, 4, 42, 8 and 50 in that order. The driver is currently serving a request at a cylinder 24. A seek takes 6 msec per cylinder moved. How much seek time is needed for shortest seek time first (SSTF) algorithm?Correct answer is '0.42'. Can you explain this answer? for GATE 2024 is part of GATE preparation. The Question and answers have been prepared according to the GATE exam syllabus. Information about A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come to the disk driver for cylinders 12, 26, 24, 4, 42, 8 and 50 in that order. The driver is currently serving a request at a cylinder 24. A seek takes 6 msec per cylinder moved. How much seek time is needed for shortest seek time first (SSTF) algorithm?Correct answer is '0.42'. Can you explain this answer? covers all topics & solutions for GATE 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come to the disk driver for cylinders 12, 26, 24, 4, 42, 8 and 50 in that order. The driver is currently serving a request at a cylinder 24. A seek takes 6 msec per cylinder moved. How much seek time is needed for shortest seek time first (SSTF) algorithm?Correct answer is '0.42'. Can you explain this answer?.
Solutions for A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come to the disk driver for cylinders 12, 26, 24, 4, 42, 8 and 50 in that order. The driver is currently serving a request at a cylinder 24. A seek takes 6 msec per cylinder moved. How much seek time is needed for shortest seek time first (SSTF) algorithm?Correct answer is '0.42'. Can you explain this answer? in English & in Hindi are available as part of our courses for GATE.
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A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come to the disk driver for cylinders 12, 26, 24, 4, 42, 8 and 50 in that order. The driver is currently serving a request at a cylinder 24. A seek takes 6 msec per cylinder moved. How much seek time is needed for shortest seek time first (SSTF) algorithm?Correct answer is '0.42'. Can you explain this answer?, a detailed solution for A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come to the disk driver for cylinders 12, 26, 24, 4, 42, 8 and 50 in that order. The driver is currently serving a request at a cylinder 24. A seek takes 6 msec per cylinder moved. How much seek time is needed for shortest seek time first (SSTF) algorithm?Correct answer is '0.42'. Can you explain this answer? has been provided alongside types of A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come to the disk driver for cylinders 12, 26, 24, 4, 42, 8 and 50 in that order. The driver is currently serving a request at a cylinder 24. A seek takes 6 msec per cylinder moved. How much seek time is needed for shortest seek time first (SSTF) algorithm?Correct answer is '0.42'. Can you explain this answer? theory, EduRev gives you an
ample number of questions to practice A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come to the disk driver for cylinders 12, 26, 24, 4, 42, 8 and 50 in that order. The driver is currently serving a request at a cylinder 24. A seek takes 6 msec per cylinder moved. How much seek time is needed for shortest seek time first (SSTF) algorithm?Correct answer is '0.42'. Can you explain this answer? tests, examples and also practice GATE tests.
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