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As is well known in the industry, cooling comprises one of the biggest problems in embedded computing. Although use of multi-core and low power RISC processors has somewhat mitigated the issue for applications and systems that do not require massive computing power, other applications are still faced with the daunting task of keeping components cool without incurring major costs. Data centers, which may include hundreds or even thousands of rack mounted “pizza box” servers, are particularly impacted by this problem. Air cooling is often insufficient, particularly in larger installations in warmer climates, and liquid or spray cooling has, until now, been both cumbersome and expensive.
It now appears that a solution is not only on the horizon, but is on the verge of being readily available.
A small company called Green Revolution Cooling, based in Austin, Texas, has developed a novel approach to liquid cooling utilizing a bath of a specific, but non-proprietary, formulation of dielectric mineral oils called GreenDEF. With GRC’s solution, the servers are mounted vertically and totally submerged in the coolant bath. The firm claims that their system can reduce cooling energy costs by ninety to ninety-five percent, and also reduce server power by ten to twenty percent! That sounds almost too good to be true.
The proof of the pudding is in the eating. Intel has, over the past year or so, conducted a fairly rigorous test of the GRC system at its Rio Rancho NM facility. The firm submerged seven servers in GreenDEF, rigged such that the oil would circulate through them (GRC’s CarnotJet system circulates the oil through a pump module and heat exchanger). Seven other identical servers utilizing air cooling were run as controls, and both batches were subjected to the same workloads.
Typically, when air cooling is employed, the cooling means consumes an overhead of approximately sixty percent of additional energy (above that required to run the servers). Intel found that the overhead required by the GRC solution was only two to three percent. In addition, because the servers were maintained at an almost constant temperature, their performance and reliability were enhanced. When the servers were disassembled after a year of use, they showed no detrimental effects from the oil bath submersion. In fact, servers remain cleaner than their air-cooled counterparts because the circulating oil carries away dust which might otherwise accumulate; dust can decrease operating efficiency by as much as two percent, and also cause premature failure.
GRC claims that the only modifications required to prepare a typical server for use with CarnotJet is removing the fan and the conductive grease between the processor and its heat sink, and sealing the hard drive. The facility in which they are to be used need not have chillers, raised floors or other special architectural features. Servers can continue to operate for several hours even in the case of a failure of air conditioning power.
Is there a down side? Well, yes – if a server requires maintenance it must be drained of the oil, which can be a bit messy. However, the GreenDEF itself is rated 0-1-0 by the NFPA (presents no health hazard, high (343° C) flash point, stable even under fire exposure conditions and not reactive with water).
I’ve saved the best for last. It costs less to build a facility utilizing CarnotJet than one that utilizes air cooling and, in many installations, there is a one-to-three year payback in energy savings alone.
I know that this blog sort of sounds like a commercial, but I’m quite impressed. If this is as good as is claimed, one of the industry’s biggest problems may be finally going away.
Word is that SuperMicro plans to offer “oil ready” servers in the fairly near future.