Selecting an Industry-Standard Metric for Data Center Efficiency

Selec ting an
Industry-Standard
Metric for Data
Cent er Efficiency
By Neil Rasmussen
White Paper #157


Executive Summary
The development of standards for the measurement and specification of data center
efficiency is an essential step in the global effort to reduce the environmental impact of
data centers. This paper explains some of the metrics that have been used to describe the
efficiency of data center physical infrastructure and suggests which metric is the most
effective.




©2008 American Power Conversion. All rights reserved. No part of this publication may be used, reproduced, photocopied, transmitted, or stored in any retrieval system of any nature, without the written permission of the copyright owner. www.apc.com WP157 Rev 0 2Introduction
In today's environment, it is good public policy and good business to consider the options to control data center energy consumption. A 1MW high-availability data center can consume $20,000,000 worth of electricity over its lifetime. Recent articles suggest that for some customers the cost of electricity is greater than the cost of IT hardware. Many companies are beginning to consider the carbon consumption of their ongoing operations and realizing that data centers are significant contributors to the environmental burden of business and industry. Research by APC-MGE and others is showing that efficiency varies widely across similar data centers, and - even more significant - the actual efficiencies of real installations are well below the practical achievable best-in-class values. The result is a strong desire among users, manufacturers, and public policy makers to incent and realize improved electrical efficiency in data centers. In this paper, we will focus on the power consumption and efficiency of data center power, cooling, and other miscellaneous infrastructure, which consumes 50% or more of the electrical power in a typical installation. The power consumption and efficiency of the IT equipment supported by the infrastructure, while critically important to overall energy use, is not the subject of this paper. Efficiency metrics are needed to allow users to compare alternative scenarios, to allow specific data centers to be benchmarked against similar facilities, and to measure progress against internal or external targets.
Holistic View of Data Center Efficiency
In a whole-system view, the data center takes in watts and performs useful computing (Figure 1). Within the data center, there are two major subsystems: (1) the data center's infrastructure, which provides support and protection for (2) the IT equipment, which performs the real "work" of the data center.
©2008 American Power Conversion. All rights reserved. No part of this publication may be used, reproduced, photocopied, transmitted, or stored in any retrieval system of any nature, without the written permission of the copyright owner. www.apc.com WP157 Rev 0 3Figure 1 - Basic elements of data center efficiency analysis
Data center
Infrastructure IT Servers Power StorageWWaattttss Cooling IITT wwaattttss Networking IINN LightingPhysical security Useful computing Fire protection Data cente r INPUT Data center OUTPUT Also called : Also called: Power IN IT output Also called: Also called: Total power consumed Useful work Total inp ut power Physical infrastructure IT power demand Useful computing work Facility input watts Site infrastructure IT power Total inc oming power Facilities IT load NCPI (IT) critical power load Critical load Using the model in the above figure, overall data center efficiency can be represented by the following simple equation: Useful computing Overall data center efficiency = Watts IN This basic view of data center efficiency, with the two-part internal breakdown shown in Figure 1, forms the foundation of the data center efficiency research and analysis currently being done by the US EPA and the EC Directorate-General. The two components of data center efficiency: Infrastructure efficiency and IT efficiency Overall data center efficiency can be logically and mathematically sepa... [download for more]