GATE CSE 1999 | Question: 1.10

Question

Which of the following disk scheduling strategies is likely to give the best throughput?

• A. Farthest cylinder next

• B. Nearest cylinder next

• C. First come first served

• D. Elevator algorithm

Comments

what is Farthest cylinder next algorithm

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Option (B) and (D) both are acceptable. For more details please check comment of @Vicky rix ji.

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As throughput is asked can it be interpreted as at any point of time during disk scheduling which Algo gives max request processing per second. Which implies minimum head movements.

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@tusharp It should be minimum head movements not maximum as overall seek latency is minimum when head movements are minimum thus maximum throughput.

Answer 1

A- Like always choose more distance from itself , so it can't be answer

B- its SSTF

C- its FCFS

D-Its SCAN

> FCFS throughput is less then SSTF so it's also not answer

> now the fight b//w SSTF and SCAN

SSTF always serve nearest cylinder first , so necessary movements gets reduced . and in case of SCAN it goes to one end and come back ,which takes more time to complete task , so SSTF throughput is best .

Answer 2

D.

Both the Nearest Cylinder and Elevator are high on throughput.But I will go with ELEVATOR.

Reason:

Nearest Cylinder Next algo will have a overhead of computing the nearest cylinders of the queue.