Greening the Cloud

The cloud has become an essential part of our daily lives. We use it to store our documents (Dropbox), to stream our music and lms (Spotify and Net ix) and without giving it any thought, we use it to work on documents in the cloud (Google Docs). The cloud forms a massive storage and processing system for an increasing amount of our digital activities. Not only consumers, but companies too are using the cloud more and more for the storage of data and to host software applications in. Behind the virtual cloud is a world of physical data centers, connected globally, packed with servers that enable us to store documents, use processing power and send data regardless of where we are or which device we use. These data centers consume a large amounts of energy, comparable with the amount consumed by the aviation industry. Although data centers work on saving energy, in particular by means of e cient cooling techniques and energy e cient servers, the growing demand for data center capacity makes it hard to realise absolute energy savings. Whereas on the one hand servers are rapidly becoming more energy e cient, this e ect is cancelled out by software that consumes increasing amounts of energy. It is expected that as a result the energy consumption of (new) data centers will keep rising in the future. Solutions with energy e cient cooling techniques end renewable energy are in- su cient. Most energy savings of hardware can be achieved by looking at the source of the energy load: the software that runs on the hardware. After all, it is the software that controls the processors, the memory, the network ports and all other components of the server.