In my last column, The Liquid Data Center, I quoted a Liebert spokesperson as saying “within a couple of years, somebody will have something where you can plug [a line containing liquid coolant] directly into a processor.” SprayCool Inc. was quick to point out that it already offers direct liquid cooling technology.
This week I had a chance to see SprayCool's liquid cooling system up close. The unit, on display at The Uptime Institute's Symposium 2007 in Orlando, consists of a control box mounted at the bottom of the cabinet, a "riser" that circulates a dielectric liquid coolant, and feed tubes emanating from the riser that routes liquid coolant to a sealed plate mounted on top of the CPU on each rack-mounted server. The liquid feed turns to gas as it picks up heat from the processor. The gas is in the return tube is then condensed and the heat exhausted, presumably into the hot aisle.
Since it focuses on one component in the server - the CPU - this system doesn't eliminate the need to air cool the racks. Also, the heat removed from the CPU is exhausted by the heat exchanger into the room air, and still must be removed by the computer room air conditioning systems.
SprayCool has been selling these devices to the government for years, as a way to reduce the required air flow through computing systems used in harsh environments. As heat and power issues gain attention in the data center, it's hoping for more commercial customers.
While the technology is an interesting retrofit for existing servers and racks, it is essentially a bolt-on, spot cooling solution. The routing of two pieces of flexible tubing to each server CPU is visually startling - it looks as as though your processor is on life support in the ER - and the tubing tethers each server to the riser. Removing a server involves disconnecting a hose from the riser fitting that looks a bit like that used on a compressor hose. In the process some liquid is likely to spill out, the spokesperson admitted. But, she said the liquid is non-conductive and evaporates rapidly.
A more wholistic approach to the problem is needed that takes into account overall power and cooling needs at the server, rack and data center itself. I suspect that major system vendors like HP and IBM will need to provide taps for liquid cooling feeds on their servers before most data centers will consider this option. That, according to the Liebert spokesperson, is already in the works.