HP's rack attack: Liquid cooling

Hewlett-Packard rolled out a new rack system that taps into chilled water from air conditioning units. HP is the third major server vendor in the past several months to introduce liquid cooling back into the data center.

Today Hewlett-Packard joined the ranks of IBM and other server vendors by turning to liquid-based systems to ease server cooling headaches.

The HP Modular Cooling System (MCS) uses a building's existing chilled water supply to distribute cool air across the front of a standard HP 10000 G2 rack.

For more information:

Egenera rolls out new blades, liquid cooled chassis

Cool aid or Band-Aid?

HP claims that the MCS allows for the deployment of up to 30 kilowatts in a single rack. That's three times the amount of kilowatts that a standard server rack can handle according to Paul Perez, vice president, power and cooling at HP.

According to Perez, data centers haven't changed in 20 years, but IT requirements have, putting strain on cooling and power demand. Now, more companies are investing in liquid cooling to meet the requirements of denser, hotter machinery that can't be cooled by air alone.

HP has been investing research dollars in heat sinks, fans and software to curb the heat problem, but now there's a new sweet spot. "With water cooling you can now mount three times the processors in a rack, and customers won't need a raised floor," Perez said. "In the next two years, I predict there will be a standard for liquid distribution in the data center."

Experts agree traditional cooling will no longer cut it. "Intel chips run too damn hot," says Clay Ryder, president of Union City, Calif.-based Sageza. "If you look at performance gains over the past few years, they've come from putting more transistors on a die and pumping up the clock rate. Thermodynamics has caught up with us."

According to Ryder, pumping more electricity through a tighter circuit increases pressure and causes friction -- which translates into heat. But liquid has more conductive properties and is more efficient at cooling than air.

Six months ago, IBM unveiled a chilled water technology that hinges onto the back of an xSeries rack. And last week, Marlboro, Mass.-based blade specialists Egenera partnered with Columbus, Ohio-based Emerson Network Power to roll out a liquid refrigerant-cooled blade chassis.

Emerson and Egenera are both quick to point out that the Liebert XD system used in the Egnera blades is different from chilled water systems. Instead of water, the Liebert XD pumps liquid refrigerant (R134a) that is converted to a gas within the heat exchangers, and then it is returned to the pumping station where it is re-condensed to a liquid.

Ryder says water and liquid refrigerants have pros and cons:

  • Because a refrigerant changes phase from liquid to gas it's easier to pump than water, saving energy on pump efficiency.
  • Water is cheaper and easy to replace.
  • If water leaks it can damage equipment. If your refrigerant leaks, you won't have gallons on the floor, but your rack could burn up anyway.
  • Many rooms already have chilled water lines coming in and facility engineers are familiar with the systems.
  • The plumbing involved with water based systems make them less reconfigurable than refrigerant-based cooling that uses tubing and closed circuit systems.

    Perez claims the HP system has some differentiation over its competitors. "The MCS is general purpose and works across all of our families of servers. Egenera's product is designed to work for only its blades," Perez said. "And our water system runs at very low pressure, 15 PSI. IBM's Cool Blue runs much higher, around 60 PSI, and that eats up pump efficiency."

    Customers can install the MCS systems themselves if they have the expertise, or they can have HP install it as part of the company's recently announced data center assessment and design services.

    Critics of such programs suggest data center services from vendors such as Dell, HP and IBM are part of an agenda to sell products. Perez said he understands that concern and noted that the HP services are based on optimizing existing infrastructure -- but if it results in HP sales that's OK with him too.

    The HP chilled water cooling systems cost around $30,000 and are expected to be available Feb. 6.

    Let us know what you think about the story; e-mail: Matt Stansberry, News Editor

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