With utility power disruption likely to become more frequent in the near term, data center managers should be motivated to design their infrastructure with power availability in mind, including redundant power distribution and generation systems to protect against system failure in the face of commercial power interruptions.

Clearly, you need to design your infrastructure to be as efficient as possible (even taking steps like specifying high-efficiency power supplies in servers). But the degree to which you can green your power distribution infrastructure will depend upon the value of continuous availability to your organization and the costs of expanding capacity. For example, our supercomputing mission at the ERDC requires very robust availability of our computers. Our electrical distribution infrastructure features redundant switches, batteries and electrical generators. These enable us to perform routine maintenance without exposing operations to an interruption, as well as to continue emergency operations over long periods during which a failure in one of these components might be expected. This increases our fixed electrical losses, but is unavoidable given our operational requirements.

3. Improve flexibility by designing for closely coupled cooling.
Computers are very efficient at two things: crunching numbers and turning electricity into heat. About 30 percent of the power that goes into the data center is turned into heat inside servers.

The traditional approach to cooling puts large chillers outside the facility to cool water, which is then pumped to computer room air-conditioning (CRAC) units on machine room floors. This approach essentially floods the entire room with cold air and offers very little flexibility for targeting specific hot spots.

The concept of "closely coupled cooling" has moved in and out of fashion over the years in supercomputing centers; we have found it to be efficient and effective. The idea is to put cooling very near the source of the heat it is meant to remove. This approach allows for targeted cooling and control of hot spots, and can result in shorter air paths that require less fan power to move the cold air around the room. Closely coupled cooling can allow for rack densities of up to four times the density of a typical room-oriented cooling solution. As customer demand pushes rack densities up, all the major server vendors are now offering closely coupled configurations.

There are many rack- and chip-based closely coupled cooling solutions. For example, there are designs that install cooling in a rack form factor alongside server racks, or place it at the top of each rack for a "top to bottom" approach. There are also solutions that deliver chilled water directly to the rear door of racks, or interleave coolers in drawers inside racks alternating with drawers of computers.