Chip-based cooling solutions come in two basic varieties. The simplest deliver cool water to one or more radiators located over heat sources in your server. More complex systems use inert liquid that is directly applied to server chips in a closed loop system. Although this technology has only recently been adopted for commodity servers, the supercomputing industry has been using this technique for decades. The ERDC supercomputing center was using chip-level vaporization heat exchange in some of its Cray supercomputers last year.

All of these options require plumbing for chilled water right to the computer racks, and you need to plan for this as you are designing your data center plumbing. If the thought of moving water into the heart of your data center causes your heart to skip a beat, fear not: There is a large body of engineering knowledge about how to minimize the risks. You'll want to take steps like keeping your water pipes a low as possible under your raised floor, installing leak detectors, isolating electrical runs from plumbing pipes, and providing leak-containment features like gravity drains and drip pans.

4. Think about the floor tiles: It's the little stuff that matters.
If you are not planning or cannot plan for closely coupled cooling, there are still steps you can take to improve the efficiency of your cooling.

Plan to minimize the profile of cables and pipes you put under the raised floor in your machine room. This is the space that your CRAC units are using to push cold air toward your computers, and the effectiveness of energy used in cooling can be greatly increased if you can minimize the interruptions that air encounters. Minimizing under-floor obstructions can also help eliminate data center hot spots and prevent air handlers from working against one another.

Another step you can take is to commission a fluid dynamics study of your data center or buy the software you need to perform that study yourself. This approach uses a computer model to simulate the flow of air around your data center and can help you identify the causes of and solutions to cooling problems, including the optimum placement of perforated floor tiles.

The ERDC supercomputing center adopted this approach several years ago to make sure we were getting the most out of our cooling. Perforated tiles are often simply lined up in front of the racks on the cold aisle of servers in a data center. "Surprisingly," says Paula Lindsey, integration lead for the center, "the most effective placement of perforated tiles isn't always right in front of the machine." The fluid dynamics study showed that we needed to increase the diameter of perforations in some tiles, and concentrate additional courses of perforated tile in critical areas.