Energy-Efficient Computing and Data Centers

Introduction

As shown by a recent news article in Nature (Jones 2018), data centers consume about 1% of the total electricity demand while information and communication technology (ICT) as a whole, including personal devices, mobile networks and TV consumes about 10%. It shows also that the demand will grow exponentially in the near future leading in 2030 to a ratio of electricity demand varying depending on the estimations between 3% and 8% for data centers and between 8% and 21% for ICT An article in the Guardian (2017) shows a similar accelerating trend.

The energy consumed by a data center during a given period is the sum of the energy consumed by all the workloads that have been executed, plus the energy consumed when devices are idle, plus the energy loss to convert the electricity from the power lines down to the IT devices, plus the energy to cool the IT devices. This book will tackle of all four aspects of energy.

The energy consumed by a workload when running on a system is the integral of its power consumption over its execution time from beginning to end. If the power consumed by the workload is constant, it would simply be:

One trivial way to minimize the power of a workload while running on a system is to reduce the frequency of the processor. But this can be counterproductive since the elapsed time will very often increase to a point where the total energy is constant ...