Liebert: High Density Will Drive Liquid Cooling
Will liquid cooling ever become a mainstream data center technology? Liquid solutions have shown modest growth in recent years, but resistance remains high in some quarters. A recent SearchDataCenter survey found that 65 percent of respondents said they would never use liquid cooling in their data center.
But the growth of high density blade server installations and virtualization may prompt a change of heart over time, according to Fred Stack, the vice president of marketing at Liebert Precision Cooling, a unit of Emerson Network Power. "The high-density cooling solutions are no longer a small experiment or niche market," said Stack. "It is becoming a principal design embraced by many industries out there. There are still a fair number of data center operators that tend to spread out rather than design for high capacity. There's some that have that extra (data center) capacity, but that number is shrinking fast. Some people are limited by the (power available from the) utility company."
Since cooling represents a large chunk of the energy usage in many data centers, it is a critical focus for managers seeking energy efficienct gains. But there are many strategies to choose between when optimizing data center cooling. At what level do you optimize, for instance: at the room level, the rack level, or even the chip level? There are also choices of cooling agent: air or liquid? If it's liquid cooling, water or refrigerant?
There's no "one approach fits all" solution, according to Stack. "One of the first questions is whether you're going to solve the problem on a rack basis or a room basis," said Stack. "Then there's the question of what kind of fluid to use. A very high percentage of the market is going to open architectures and pump refrigerants."
Liebert offers products to support both rack-level (closed) architecture and water cooling. But Stack said Liebert sees refrigerant-based cooling in an open architecture as the best approach for the majority of the growing number of high density installations.
"An open architecture is the most forgiving," said Stack. "There are places where closed architecture is the right approach. These tend to be focused situations dealing with a small number of particularly high density racks. For any application that's gone high density, more than 8 kilowatts a rack, you get into fluid cooling."
As for the cooling medium, Stack references the ongoing debate about "data center hydrophobia" – the fear of introducing water into the equipment area after years of policies that banned liquids from raised-floor space. "The pump refrigerants are the collective choice, because of people's fear of water and electricity," said Stack. "That dates back to the mainframe days."
Any discussion of water cooling usually includes a reference to the days of water-cooled mainframes. This history is typically invoked as an argument in favor of water - that the industry has "been there and done that" and that current fears of water cooling are overdone. But Stack sees it differently, arguing that the mainframe-era experience featured enough challenges and mishaps with water cooling to justify a different approach.
Liebert's XD line of "extreme density" cooling products use a refrigerant known as R134a, which changes phase from liquid to gas, making it easier to pump than water and minimizing the impact from potential leaks. Stack said the refrigerant's heat transfer is more efficient than water. Liebert XD is currently deployed on more than 6,000 racks at 350 customer sites, Stack said.
While blade servers have been a primary driver for companies adopting liquid cooling, there may soon be another: virtualization. Many companies are looking to virtualization to maximize the gains from server consolidations. The result is a smaller footprint, but usually with much higher density.
"There's no question that one of the reasons many of the OEMs are embracing us right now is the growth of virtualization," said Stack. "The XD system helps enable blade servers. We've shown that you don't have to be afraid of blade servers. The same thing is true with virtualization. If I get a more dense set of applications, I need to cool the zone."
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By Rich Miller 
September 05, 2007 | Permalink | >Get Posts By E-mail
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