1) Consider a disk with an advertised average seek time of 3ms, rotation speed o
ID: 3860167 • Letter: 1
Question
1) Consider a disk with an advertised average seek time of 3ms, rotation speed of 20,000rpm and 512 byte sectors with 500 sectors per track. Suppose we wish to read a file consisting of 2000 sectors.
a) Assuming that the data is stored as compactly as possible so that we only need one seek time to locate the first track and no additional seek time is needed, calculate the total transfer time.
b) Assuming that the data is spread amongst disparate tracks and sectors, so the time to read the next sector requires a new seek time, calculate the expected total transfer time.
Explanation / Answer
Since the disk rotates @20000 rpm
time required for 1 rotation = 3ms
So avg rotational time = 1.5ms
avg seek time = 3ms
sector reading time = 3/500 ms or 0.006ms
to read 2000 sector (stored as compactly as possible):
seek: 3ms
avg rotational delay: 1.5ms
read time: 0.006*2000ms = 12ms
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total time: 16.5ms
to read 2000 sector (spread amongst disparate tracks and sectors):
seek: 3ms * 2000
avg rotational delay: 1.5ms * 2000
read time: 0.006*2000ms = 12ms
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total time: 9012ms
Ihope this will help you!
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