The Green Grid definition for DCiE (or DCE) is IT Equipment Power/Total Facility Power1, as shown in Figure 1. This metric does not adequately account for power and cooling management innovations that reside within the IT equipment itself, and the industry needs to evolve the definition to properly affect buyer behavior.
Typical IT facilities have a DCiE rating of 50%; in other words it takes as much energy to power and cool the equipment (HVAC, UPS, etc) as it does to run the core equipment (servers, storage, network, etc and the associated power and cooling management technologies embedded within this equipment-- e.g. fans).
However, this definition does not lead to the optimum green behavior. The reason is that by definition, cooling and power management that is embedded within the IT equipment will be counted as part of the IT portion of the DCiE equation.
For example, Verari Systems2 has introduced innovative green technology that changes the way air is moved in server racks from front-to-back to bottom-to-top. This significantly reduces the number of fans and the power required to move air through the rack. This technology will clearly lower power requirements and make a facility more efficient. However, the fan power saved from this cooling efficiency will not improve the DCiE score, as it lowers both the numerator and denominator of DCiE as defined in Figure 1, maintaining the same DCiE score.
For a metric to be effective as part of government policy and/or as an organizational objective, it should motivate appropriate behavior. Any organization or individual motivated by improving DCiE as an incentive might reject Verari's energy-saving technology. As such, cooling and power management efficiencies derived from innovations that reside within the IT equipment itself should be isolated and included in the non-IT portion of DCiE calculations and not the IT component.
Action Item: The Green Grid should change the IT equipment definition of DCiE to include only the energy to power the core equipment. The power supplies and fans should be defined as part of the total facility power (the denominator) and not part of the numerator. Vendors should include both the core power consumption measurements as well as the total consumption measurements as part of specifications.
Footnotes: 1 Source: Green Grid at www.thegreengrid.org Downloaded 12/24/2008
Sadly Verari is no longer trading as of December 2009