Consider a disk with 16384 bytes per track having a rotation time of 16 msec…
2015
Consider a disk with 16384 bytes per track having a rotation time of 16 msec and average seek time of 40 msec. What is the time in msec to read a block of 1024 bytes from this disk?
- A.
57 msec
- B.
49 msec
- C.
48 msec
- D.
17 msec
Attempted by 79 students.
Show answer & explanation
Correct answer: B
Solution: compute the seek, rotational latency, and transfer time and add them.
Average seek time = 40 ms.
Average rotational latency = half the rotation time = 16 ms / 2 = 8 ms.
Transfer rate per ms = 16384 bytes / 16 ms = 1024 bytes/ms, so time to read 1024 bytes = 1024 / 1024 = 1 ms.
Total time = seek + average rotational latency + transfer = 40 + 8 + 1 = 49 ms.
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