Water is known to be thousands of times more efficient at dissipating heat than air and years ago was the means of cooling mainframes in data centers. But as IT infrastructures moved away from mainframes and toward distributed environments, air cooling became more prevalent. With the Power 575, IBM has announced that cooling may come full circle.
"Liquid cooling was actually quite common in the late '80s and early '90s, with companies dealing with the first wave of heat-related issues in data centers," said Charles King, an analyst at Pund-IT Inc. "More recently there has been a significant resistance to liquid, but it's so much more efficient a cooling system than air."The barrier for liquid cooling
There are some signs that liquid cooling is taking hold, but data center managers remain reluctant. In a SearchDataCenter.com purchasing intentions survey last year, more than 60% said they don't use liquid in their data center and have no plans to do so. But in a recent Uptime Institute survey, about one-third of respondents said they are or will use liquid-cooled cabinets. And in its report to Congress last year on data center power consumption, the federal Environmental Protection Agency said that "direct liquid cooling" could lead to an 80% improvement in facility energy efficiency.
It's not that data center cooling systems don't include any water at all. In both raised-floor and overhead facility cooling infrastructures, water is piped into the computer room air conditioners (CRACs), which then blows cold air to the servers. Vendors like Emerson Network Power and American Power Conversion Corp.(APC) also build cooling systems that sit on top of or in between racks that have water piped to them, and IBM has the Rear Heat Door eXchanger, which attaches to the back of the rack and acts like a car radiator for IT equipment.
Still, IT departments have become jittery about placing water too close to IT equipment.But the 575, which runs AIX and Linux and will be available starting next month, may dispel those fears. The new Hydro Cluster, as IBM calls it, includes the following features:
- It includes 14 servers that include 16 dual-core 4.7 GHz Power6 processors each, with a total of 224 processors and 448 cores.
- Up to 256 GB of RAM per server, for a total of about 3.5 TB of memory in a single server cabinet.
- Water piping that threads through the rack and into the server, including water-chilled copper plates that sit on the processor heat sinks.
- The ability to run AIX, Novell SUSE Linux Enterprise Server, and Red Hat Enterprise Linux.
Here is a video of the cooling in action:
"Obviously we're not just using garden hoses or pipes you use in your house," said IBM Power Systems General Manager Ross Mauri. "All couplings and connectors are high-end leak-proof, and there is active monitoring on all water valves and pressure."
Threaded throughout the entire rack, the piping pumps in cold water to the chips and pumps out the resulting hot water away. IBM is promoting the idea of then using the warmed water for other means, such as heating a nearby office. Mauri said that most of the IBM engineers that worked on this cooling system helped to build and maintain water-cooled mainframes back in the day.
While IBM is offering water-cooled servers, other companies such as SprayCool have cooling products using a different kind of liquid that won't ruin electronics if it touches them.
"The issues around water and electronics cause some natural concern," King said. "The fact is if the design is well engineered, any liquid should be fine. The good thing about water is it is more available and less expensive than other specialized coolants."
Will IBM start offering water-cooled versions of all its servers? Mauri said that's still a matter of speculation. He cited the company's Cool Blue Rear Door Heat eXchanger, which provides water-cooling to the back of the rack – not as close as on the processor heat sinks, but still closer than to the CRAC units. Still, the Power 575 gives IBM a chance to introduce the idea of water-cooled servers back into discussion with its customers.
"We're always looking at different types of cooling," Mauri said. "I think we'll educate folks so that the scare factor goes down.
In addition to the 575, IBM introduced the Power 595, similar to previous 595 models, but now including dual-core Power6 processors that can run as fast as 5 GHz. The machine will be able to run AIX, Linux and the newly named IBM i.