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Recent questions tagged disk-scheduling

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3 answers
1
Consider a disk system having $60$ cylinders. Disk requests are received by a disk drive for cylinders $10,22,20,2,40,6$ and $38$, in that order. Assuming the disk head is currently at cylinder $20$, what is the time taken to satisfy all the ... cylinder to adjacent one and Shortest Seek Time First (SSTF) algorithm is used? $240$ milliseconds $96$ milliseconds $120$ milliseconds $112$ milliseconds
asked Nov 20, 2020 in Operating System jothee 481 views
0 votes
3 answers
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Disk request 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 $6\text{ ms}$ per cylinder. The total seek time, if the disk arm scheduling algorithm is first-come-first-served is $900$ ms $850$ ms $360$ ms $876$ ms
asked Apr 1, 2020 in Operating System Lakshman Patel RJIT 300 views
0 votes
1 answer
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A disk has $200$ tracks (numbered $0$ through $199$). At a given time, it was servicing the request of reading data from track $120$, and at the previous request, service was for track $90$ ... (Shortest Seek Time First) and FCFS (First Come First Serve)? $2$ and $3$ $3$ and $3$ $3$ and $4$ $4$ and $4$
asked Mar 30, 2020 in Operating System Lakshman Patel RJIT 334 views
1 vote
3 answers
4
Consider a disk queue with I/O requests on the following cylinders in their arriving order: $6,10,12,54,97,73,128,15,44,110,34,45$. The disk head is assumed to be at cylinder $23$ and moving in the direction of decreasing number of cylinders. Total number of cylinders in the disk is $150$. The disk head movement using SCAN –scheduling algorithm is: $172$ $173$ $227$ $228$
asked Mar 24, 2020 in Operating System jothee 545 views
2 votes
1 answer
5
Consider the following five disk five disk access requests of the form (request id, cylinder number) that are present in the disk scheduler queue at a given time. $(P, 155), (Q,85), (R,110),(S, 30), (T,115)$ Assume the head is positioned at cylinder $100$. The ... $S$,but before $T$. The head reverses its direction of movement between servicing of $Q$ and $P$. $R$ is serviced before $P$.
asked Feb 12, 2020 in Operating System Arjun 2.1k views
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6
Write a program to implement the three disk-arm scheduling algorithms. Write a driver program that generates a sequence of cylinder numbers $(0–999)$ at random, runs the three algorithms for this sequence and prints out the total distance (number of cylinders) the arm needs to traverse in the three algorithms.
asked Oct 28, 2019 in Operating System Lakshman Patel RJIT 187 views
0 votes
1 answer
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Disk requests come in to the disk driver for cylinders $10, 22, 20, 2, 40, 6,$ and $38,$ in that order. A seek takes $6\: msec$ per cylinder. How much seek time is needed for First-come, first served. Closest cylinder next. Elevator algorithm (initially moving upward). In all cases, the arm is initially at cylinder 20.
asked Oct 28, 2019 in Operating System Lakshman Patel RJIT 282 views
2 votes
5 answers
9
Consider a disk system with $100$ cylinders. The requests to access the cylinders occur in the following sequences: $4, 34, 10, 7, 19, 73, 2, 15, 6, 20$ Assuming that the head is currently at cylinder $50$, what is the time taken to satisfy all requests if it takes $1$ ms to move from the cylinder to adjacent one and the shortest seek time first policy is used? $357$ ms $238$ ms $276$ ms $119$ ms
asked Jul 2, 2019 in Operating System Arjun 810 views
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0 answers
10
Compare the performance of $C-SCAN$ and $SCAN$ scheduling, assuming a uniform distribution of requests. Consider the average response time (the time between the arrival of a request and the completion of that request’s service), the variation in response time, and the effective bandwidth. How does performance depend on the relative sizes of seek time and rotational latency ?
asked Mar 22, 2019 in Operating System akash.dinkar12 159 views
0 votes
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11
Suppose that a disk drive has $5,000$ cylinders, numbered $0$ to $4,999$. The drive is currently serving a request at cylinder $2,150$, and the previous request was at cylinder $1,805$. The queue of pending requests, in $FIFO$ ... for each of the following disk-scheduling algorithms ? $a. FCFS$ $b. SSTF$ $c. SCAN$ $d. LOOK$ $e. C-SCAN$ $f. C-LOOK$
asked Mar 22, 2019 in Operating System akash.dinkar12 191 views
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12
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1 answer
13
None of the disk-scheduling disciplines, except $FCFS$, is truly fair (starvation may occur). a. Explain why this assertion is true. b. Describe a way to modify algorithms such as $SCAN$ to ensure fairness. c. Explain why fairness is an important goal in a ... d. Give three or more examples of circumstances in which it is important that the operating system be unfair in serving $I/O$ requests.
asked Mar 22, 2019 in Operating System akash.dinkar12 175 views
0 votes
1 answer
14
Why is rotational latency usually not considered in disk scheduling ? How would you modify $SSTF$, $SCAN$, and $C-SCAN$ to include latency optimization ?
asked Mar 22, 2019 in Operating System akash.dinkar12 142 views
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0 answers
15
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1 answer
16
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Disk request come into disk driver for cylinders 5, 17, 60, 125, 28, 170, 8, 32. Total moves using SCAN algorithm when disk head is currently positioned at 35 and moving toward higher cylinder number________.(Disk system has 200 cylinders (0 - 199)
asked Jan 21, 2019 in Operating System `JEET 200 views
0 votes
2 answers
18
1 vote
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21
Suppose a disk has 100 cylinders, numbered from 0 to 99. At some time the disk arm is at cylinder 20, and there is a queue of disk access requests for cylinders 10, 22, 6, 38, 2, 40, 20. No of seeks in FCFS SSTF
asked Dec 11, 2018 in Operating System jatin khachane 1 540 views
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0 answers
22
How does LOOK algorithm decides that this is the last request? What technique is used to determine that after this request, instead of going to the end of disk, the direction should be changed?
asked Dec 4, 2018 in Operating System Astitva Srivastava 376 views
0 votes
4 answers
23
Consider a disk has 200 cylinders, numbered from 0 to 199. At some time the disk arm is at cylinder 100, and moving towards right direction. There is a queue of disk access requests for cylinders 30, 85, 110, 100, 105, 126, 135, 55 and 195. The difference in ... by the R/W head when the LOOK algorithm is used compared to the CSCAN algorithm is ________. Please also mention the method of C-SCAN.
asked Nov 4, 2018 in Operating System Warrior 1.5k views
0 votes
1 answer
24
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25
Suppose that the head of a moving head disk with 192 tracks(0-191), is currently serving a request at track 80 and has just finished at track 62. The queue of the request is kept in FIFO order: 119, 58, 114, 28, 111, 55, 103, 30, 75. What is the total no of tracks traversed by head movements needed to satisfy these request for the Elevator disk-scheduling algorithm? a. 143 b. 130 c. 177 d. 547
asked Oct 4, 2018 in Operating System garvit_vijai 1.4k views
1 vote
2 answers
26
which topic should i need to learn under file system and disk scheduling for gate??
asked Sep 9, 2018 in Operating System gatecrack 337 views
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