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 50% capacity.

Assume further that the power does not scale linearly with the load; that is, when the servers are

operating at 50% capacity, they consume 80% 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 50% of the servers?

b. How much power savings would be achieved by placing 50% 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 25% of the servers in the

barely alive state and 25% off?