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+13 votes
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For a magnetic disk with concentric circular tracks, the seek latency is not linearly proportional to the seek distance due to

  1. non-uniform distribution of requests

  2. arm starting and stopping inertia

  3. higher capacity of tracks on the periphery of the platter

  4. use of unfair arm scheduling policies

asked in Operating System by Veteran (59.6k points)
retagged by | 2.5k views

3 Answers

+16 votes
Best answer
answered by Boss (13.6k points)
edited by
+4
I also agree with this answer.
Have drawn inferences from the link above and this paper:

An excerpt:
"A seek is composed of
• a speedup, where the arm is accelerated until it reaches half of the seek distance or a fixed maximum
velocity"

http://www2.cs.uh.edu/~paris/7360/PAPERS03/IEEEComputer.DiskModel.pdf

Though, it's a despair that the book that I encountered this question, marks the answer as C and the Gate solution key as D.

Have already wasted an hour on this question.. duh!
0

Why not use of unfair arm scheduling policies

What if SCAN or LOOK algorithms are used?

–2
can u do something better than downvoting?
0

The answer cannot be B, latency used by itself is used to refer to rotational latency and not seek time. Even then I find no other option to be suitable.

+14 votes
The answer is B , because due to Inertia

When ever your read write head moves from 1 track to another track, it has to face resistance due to change in state of motion including speed and direction ,which is nothing but inertia . Hence the answer is B
answered by Active (1.9k points)
0 votes
Answer is B

Because of the factors of acceleration and deceleration of actuator arm.
answered by (259 points)


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