You've heard about data centers in shipping containers. But how about a data center in a tent? And in rainy Seattle?

Enterprises are pushing the operating parameters that server vendors recommend for factors like air temperature and humidity -- and they're finding that servers are often far hardier than they expect. The difference can mean significant data center operations savings.

Microsoft recently found that a little rain, uncontrolled temperature and even leaves sucked into server fans had absolutely no negative effect on servers.

In a small experiment, two Microsoft employees put five servers in a large metal frame tent outside. Christian Belady, principal power and cooling architect, and Sean James, facility program manager, ran the previously used but spare HP DL585 servers in the tent from November 2007 through June 2008 and had zero failures.

"While I am not suggesting that this is what the data center of the future should look like. ... I think this experiment illustrates the opportunities that a less conservative approach to environmental standards might generate," Belady wrote in a blog post.

Enterprises have long known that server vendors give very conservative operating parameters for factors like temperature. Vendors likely do that to protect their own bottom line, even though doing so may negatively affect their customers' bottom line. "They could certify them at higher temperatures than they probably do, but they would probably see higher field failure rates," said Nik Simpson, an analyst at Burton Group. "The failures might not be significant to individual companies running those servers, but it could be to the vendor having to replace the servers for hundreds of thousands of customers."

Microsoft is not alone among companies experimenting with pushing the limits in data centers. Intel recently published a study about a data center test it conducted that relied almost exclusively on outside air for cooling. Intel installed no humidity controls and only minimal air filters.

Intel found that the test environment had a very similar failure rate to one using traditional air conditioning and humidity controls. The changes could save US$2.87 million annually for a 10-MW data center, Intel said.

Simpson expects to see companies like Microsoft and Intel that are building new Internet scale data centers continue to conduct such experiments because of the cost savings.

But using servers in this way may not be relevant to small or midsize companies that have their own data centers. "For a lot of organizations, the data center is buried deep in a building so there is no ambient air flow to use," Simpson noted. Many companies don't have the luxury of building a new facility in a handpicked location for their data centers and must make due with existing facilities.

Both Intel and Microsoft said they plan further tests that, if they show similar results, will lead to implementations in their data centers.