Simplified Power Usage in Server Farms
Given that power is expensive, it is common practice to leave servers on only
when they are being used and to turn them off whenever they are not in use.
Assume that the following power-aware algorithm is used: When a job arrives,
it instantly turns on a fresh server (assume zero setup cost). When the job
completes service, it instantly turns off that server. Assume that there is always
a server available for every job (i.e., there is no queueing). Your goal is to derive
the time-average rate at which power is used in our system. Assume that when
a server is on, it consumes power at a rate of P = 240 watts. Assume λ = 10
jobs arrive per second and that the service requirement of jobs is Uniformly
distributed ranging from 1 second to 9 seconds.
(Note: This is a highly simplified model. We will study much more complex
models in Chapter 27.)