Question

Given that the time to read data off a 7200 rpm disk drive will be roughly 75% of a 5400 rpm disk, at what idle time of the 7200 rpm disk will the power consumption be equal, on average, for the two disks?

Answer 1

Answer:

Given that the time to read data off a 7200 rpm disk drive will be roughly 75% of 5400 rpm disk, at 30% idle time of 7200 rpm disk will the power consumption be equal, on average for the two disk

Explanation:

Let the 7200-disk busy time = x  ( we need to calculate it)

As given in the question the in the given time to read data off a 7200 rpm disk drive will be roughly 75% of 5400 rpm disk. This mean that we equalize the equations of both disk power

7200-disk power      =     5400-disk power

here we apply the formula to calculate the 7200 rpm disk busy time

4.0 * (1-x) + 7.9 * x      =     2.9 * (1-x/0.75) + 7.0 * x/0.75

4.0 + 3.9 x                  =      2.9 – 3.87 x + 9.33 x

1.1                                =        5.47 x – 3.9 x

we calculate the value for x

Hence                   x = 0.70

Applying formula to calculate the idle time.

Idle time = 1.0 – 0.70 = 0.30