Microsoft's "cloud" starts close to the ground.

The company is building a global system for delivering Internet services, which Chief Software Architect Ray Ozzie explained in some detail last month.

The first component is what Ozzie called "global foundation services" consisting of the company's 20 data-center locations around the world, racks of computers and disks inside the data centers, the network that connects them to the Internet, and the workers who build, operate and maintain them.

"The data centers are of massive scale," Ozzie said at Microsoft's Financial Analyst Meeting. "... They're built with commodity components, and that's how you get the cost down, and they achieve reliability through redundancy, not the fail-safe nature of any given component within the data center," Ozzie said.

With the company racing to move toward a new software-delivery model that relies heavily on Internet services, it is adding data-center capacity to keep pace.

"Our deployed servers and infrastructure has more than doubled over the course of the past year, and we will keep investing," Ozzie said.

In the past month alone, Microsoft began construction on a data center in San Antonio and purchased another in Santa Clara, Calif., it had been renting.

In Quincy, Grant County, the first portion of what will become its largest data center went online this year. It will potentially grow to six buildings, totaling 1.5 million square feet.

The rest of the cloud is a complicated, multilayered collection of software that puts this huge accumulation of computing horsepower to work.

One layer balances loads and optimizes performance of the data centers. There is software to handle different types of searchable storage that end-user applications will ultimately call on (think of the e-mails sitting in the in-box of a Windows Live Hotmail account). This layer also contains software for quickly and efficiently delivering the applications and content to Internet users around the world.

The next layer contains software that performs several functions drawn on by multiple end-user applications — primarily those aimed at consumers and small businesses — such as verifying an individual's identity and allowing him or her to log in to e-mail, instant messaging, blogging and online storage.

This layer includes software that manages contact lists, the various devices individuals use to access these services and security.

"Perhaps most importantly, our advertising-platform infrastructure lives at this level," Ozzie said.

The final layer carries the applications themselves.

Current applications include the Xbox Live network, with features such as in-game instant messaging; Office Live, a set of services geared toward small businesses; and Windows Live, a sprawling set of communications tools for consumers.

The company has more on the way. Later this fall, for example, it's planning to begin selling a version of its customer-relationship-management software for businesses that will make use of this same cloud system.

— Benjamin J. Romano