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Tripping On Power: Page 3 of 14

The conclusion here is self-evident. High-density deployments will require a substantial investment in new power and cooling systems, and that means AC, electrical wiring, UPSs, and generators. To that end, the Meta Group recommends that new data centers be designed to support 500W/sq ft. But rare is the data center that meets this criterion, and even if it did, and even considering aisle clearances, that's less than half the power our full rack of HP blade servers would require.

Nonetheless, Frountan says Rackspace designs its facilities so that its racks can be filled. He agrees with the 500W/sq ft recommendation and offers some additional advice: "It's typical to design cooling systems with N+2 or N+3 redundancy, but what happens if three chillers or blowers next to each other fail? You'll also need to make sure adjacent cooling systems aren't on the same electrical bus." When sizing cooling systems for each rack, he recommends oversizing by 10 to 15 percent. "If you remove exactly 10kW of heat from a rack of equipment that produces 10kW, it will remain at temperature, but it won't cool down. If it gets up to 100 degrees while techs have doors open, the extra cooling will return it to operating temperature quickly."

SPREAD IT OUT

For existing data centers, the notion of fully packed racks pumping out trillions of compute cycles per second or storing hundreds of terabytes is an attractive one, but not very practical. A more realistic arrangement is to spread out the equipment and leave a good bit of open rack space.

We stated at the outset that in a great many cases, existing power and cooling systems are adequate to support the gross loads presented to many data centers. While that's true, what's new is that spot loads, both for cooling and power, will easily outstrip the design of current data centers. Power can be moved around, but cooling is another matter.