The Microsoft facility will sprawl across about 12 acres of floor space and may have as many as 440,000 servers in the 220 containers that are being installed. And that's just on the first floor; an undisclosed number of additional systems will be installed on the second floor, which will have a traditional raised-floor layout.

But with just 35 full-time employees divided among the equivalent of four work shifts at the 24/7 facility, the average number of on-site staffers likely won't break double digits. "Working at a Microsoft data center can be a lonely experience," Manos said. Microsoft has similar workforces at some of its other data centers, but Manos noted that those are much smaller than the new facility will be, in terms of both systems and floor space.

The impact of massive data centers like the one Microsoft is building, and the added online services that they may make possible, won't be felt quickly within IT departments. "People don't change their e-mail systems overnight," Gartner's Smith said.

Jim Bingham, CIO at the University of Kansas Medical Center, agreed that any such changes will take time within his organization. But Bingham does plan to consider external online services. "Not immediately, but definitely in the next three to five years," he said.

Vendors such as Sun Microsystems, Rackable Systems and Verari Systems are selling container-based systems. IBM and Hewlett-Packard have also developed modular data center technologies. But the appeal of cloud-based services may be limited in industries such as aerospace, defense and financial services, which all have to contend with numerous regulatory restrictions. And companies that have already installed integrated systems extensively may not see a great need to shift their server resources to outside providers.

John Enck, another Gartner analyst, said that containers -- whether they're the 20-footers that Sun is marketing, or the 40-foot-long ones that Rackable and Verari are offering -- may make sense only for companies building data centers on the same scale as Microsoft. In other words, very few. "It's about as leading-edge as you can get -- and it's not for the masses," Enck said.

Customized, special-purpose servers -- such as the ones Dell began offering last year to customers that buy more than 1,000 systems per quarter -- may be a less-extravagant alternative.

Dell tunes all the systems in advance to support the specific applications that will run on them. One of the early users is search engine vendor Ask.com, which says the custom-designed systems have reduced its hardware costs and the amount of power its servers consume.

That kind of approach could provide data center managers with some of the modularity and efficiencies that Microsoft is aiming for in its new facility, but on a more modest scale.

And even if more companies do embrace cloud-based online services in the years ahead, some users think that new opportunities will continue to open up within data centers.

After all, there is still a need for a significant number of longshoremen in US ports. In fact, as trade between the US and countries in Asia has increased, so has the demand for dockworkers, according to Craig Merrilees, a spokesman for the International Longshore and Warehouse Union, which represents about 25,000 longshoremen on the West Coast.

ILWU members worked 24 million hours in 2001, Merrilees said. But by last year, that figure had risen to just under 33 million hours.

Similarly, workers will still be needed to deal with online service providers, said Jason Dauwen, a software development manager at a company that makes software for financial services firms. "But it will probably be more business [analysts] than technical staff," said Dauwen, who asked that his employer not be identified.

DigitalChalk, a vendor of online training systems, relies on Google Apps for its internal e-mail. And last year, it began using Amazon.com's Elastic Compute Cloud service to support customer applications. But no IT staffers lost their jobs as a result of that move, said Troy Trolle, DigitalChalk's chief technical officer. Instead, they began managing the company's applications on the Amazon EC2 servers.