Layered Green Performance Indicators

This paper presents a novel approach to characterising energy consumption in IT service centres comprising the whole system view, from the IT infrastructures, to the applications and their design and execution environments. The approach is based on a set of energy-related metrics called Green Performance Indicators (GPIs) which enable monitoring the energy consumption level of the IT service centre in terms of computing resource usage, impact on the environment, costs/efforts required to develop and redesign applications and reconfiguring the IT-infrastructure. Our approach, which is framed within the EU Project GAMES [15] about green IT, defines four layers of GPIs allowing for a comprehensive description of energy consumptions at various system levels, in relation to a given Quality of Service (QoS), to impact on the environment (consumables, power, emissions, cooling systems, and so on) and to high-level business objectives. These GPI metrics are defined to measure the ''greenness'' of a computing environment, and more precisely, to detect where the IT service centre wastes energy. The monitoring and evaluation of GPIs allows the introduction of energy efficiency measures through interventions at various levels (e.g., improving IT resource usage or changing the QoS), allowing for an adaptation and optimisation of the according execution modes.