HP's move into fluid-based cooling follows IBM 's release last July of an add-on water- cooled unit for its server line. And last week, blade server maker Egenera Inc. announced an offering called CoolFrame that integrates Lie-bert Corp.'s X-treme Density (XD) cooling technology with a new 24-blade enclosure.

Liquid cooling, once a staple of mainframe-oriented data centers, is returning to the mainstream as some IT managers look for ways to keep their increasingly dense and power-hungry servers chilled.

"I think liquid cooling is here to stay, and customers will want standardization -- plug-and-play capabilities," said Paul Perez, vice president of storage, networking and infrastructure for HP's industry-standard servers unit.

Perez said HP is talking with rival vendors as well as standards organizations about the need for things such as standardized fittings for tapping into chilled water supplies. "What we're after is some consistency of experience for customers," he said.

But vendors' enthusiasm for liquid cooling will meet resistance from users like George Horvath, who manages Memorial Sloan-Kettering Cancer Center's 18,000-square-foot data center in Lyndhurst, N.J. "I'd prefer not to have any of those cabinets here," said Horvath, adding that facilities managers in particular are going to be worried about leaks. HP's Modular Cooling System is a self-cooled 42U rack that costs US$30,500 and can cool racks of blades that consume up to 30 kilowatts of power. Because the unit is self-contained, it doesn't have to be located in a data center and can be placed in air-temperature rooms, HP said.