Consider a disk with a sector size of 512 bytes, 2000 tracks per surface, 50…
2020
Consider a disk with a sector size of 512 bytes, 2000 tracks per surface, 50 sectors per track, five double-sided platters, and an average seek time of 10 milliseconds.
If the disk platters rotate at 5400 rpm (revolutions per minute), approximately what is the maximum rotational delay?
Answer: A. 0.011 seconds — ConceptRotational delay is the waiting time for the required sector to rotate under the read/write head. The maximum delay is one complete revolution; the…
- A.
0.011 seconds
- B.
0.11 seconds
- C.
0.0011 seconds
- D.
1.1 seconds
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Correct answer: A
Concept
Rotational delay is the waiting time for the required sector to rotate under the read/write head. The maximum delay is one complete revolution; the average delay is half a revolution.
Application
Convert the rotation rate to revolutions per second: 5400 ÷ 60 = 90 revolutions per second.
Find the time for one revolution: 1 ÷ 90 = 0.011111… seconds.
Use one full revolution for the maximum rotational delay, giving approximately 0.011 seconds (11.11 milliseconds).
Cross-check
Multiplying 0.011111… seconds per revolution by 90 revolutions per second gives 1, representing one complete revolution; the time and rate units cancel. Half of this period, about 5.56 milliseconds, would be the average rotational delay rather than the maximum.
Therefore, the maximum rotational delay is approximately 0.011 seconds.
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