Server farms such as Google and Yahoo! provide enough compute capacity for the h

Question

Server farms such as Google and Yahoo! provide enough compute capacity for the highest request rate of the day. Imagine that most of the time these servers operate at only 60% capacity. Assume further that the power does not scale linearly with the load; that is, when the servers are operating at 60% capacity, they consume 90% of maximum power. The servers could be turned off, but they would take too long to restart in response to more load. A new system has been proposed that allows for a quick restart but requires 20% of the maximum power while in this "barely alive" state.

A. How much power savings would be achieved by turning off 60% of the servers?

B. How much power savings would be achieved by placing 60% of the servers in the "barely alive" state?

C. How much power savings would be achieved by reducing the voltage by 20% and frequency by 40%?

D. How much power savings would be achieved by placing 30% of the servers in the "barely alive" state and 30% off?

Explanation / Answer

A, The 60% of the server takes about 90% of maximum power. but if you turn off the remaining 40% of server then you will get 40% of 90% saving that is about 36% total savings on maximum power. in the same time the 60% will operate at 100% power so it is more (60% * 10%) 6% so the answer is 30% saving.

B, with the remaining taking 20% power when turned off would save the power about 40% * 70% of maximum power saving
so it is 28% - 6% is about 22% saving.

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