Consider a disk pack with a seek time of 4 milliseconds and rotational speed…
2015
Consider a disk pack with a seek time of 4 milliseconds and rotational speed of 10000 rotations per minute (RPM). It has 600 sectors per track and each sector can store 512 bytes of data. Consider a file stored in the disk. The file contains 2000 sectors. Assume that every sector access necessitates a seek, and the average rotational latency for accessing each sector is half of the time for one complete rotation. The total time (in milliseconds) needed to read the entire file is ____________.
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Correct answer: 14020
Key idea: each sector read requires a seek, an average rotational latency (half a rotation), and the sector transfer time.
Rotation time = 60 s / 10000 RPM = 0.006 s = 6 ms.
Average rotational latency = half rotation = 6 ms / 2 = 3 ms.
Transfer time per sector = rotation time / sectors per track = 6 ms / 600 = 0.01 ms.
Time per sector = seek time + avg rotational latency + transfer time = 4 ms + 3 ms + 0.01 ms = 7.01 ms.
Total for 2000 sectors = 2000 × 7.01 ms = 14,020 ms.
Final answer: 14020 milliseconds
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