  In ours days data centers provide the global community an indispensable
service: nearly unlimited access to almost any kind of information we can
imagine by supporting most Internet services such as: Web hosting and
E-commerce services. Because of their capacity and their work, data centers
have various impacts on the environment, but those related with the electricity
use are by far the most important. In this paper, we present several power and
energy management techniques for data centers and we will focus our attention
on techniques that are explicitly tailored to servers and their workloads.
