Microsoft has opened up for business its new Dublin data centre, a massive 550,000-square-foot facility dedicated to serving primarily European customers.

Construction isn't quite done yet, with about 303,000 square feet finished, but Microsoft is accepting clients. The company will run cloud services from the centre for consumers, businesses and developers, said Steve Clayton, who works in cloud-computing strategy for Microsoft International.

On the consumer side, the data centre will run applications such as Windows Live Mail, formerly Hotmail, as well as Microsoft's other Live-branded services. Businesses will be able to subscribe to a range of hosted applications, including Exchange e-mail, the Sharepoint collaboration software and Office Communication Server, among others, Clayton said.

The Dublin facility will also host Microsoft's Azure platform, which will be made available in November. Azure is a platform that developers can use to host and manage Web-based applications.

Dublin was chosen for the data centre due to the local talent pool, robust Internet connectivity and cool climate, Clayton said.

Microsoft is using outside air to cool the data centre. One of the predominant costs for running a data centre is electricity in order to keep servers cool. The data centre's operating temperature can be maintained 95 percent of the time without mechanical or refrigerated cooling, such as chilled water systems.

"We literally take outside air and pump it directly into the server room," Clayton said.

The Dublin data center's PUE (power usage effectiveness) is 1.25, which means for every one watt of server power, there's .25 of a watt dedicated to cooling and other electricity-consuming functions, Clayton said. The industry average PUE for data centers is between 2 and 2.4 PUE. Microsoft's average for all of its data centers is 1.6, although the company wants to reduce that to 1.125 by 2012.

The facility can now generate up to 5.4 megawatts of critical power. Eventually, it will be possible to expand to 22.2 megawatts, Microsoft said.

Customers have the option of having their applications run on their own dedicated server or sharing hardware, which is a cheaper option, Clayton said. Some administrators don't like the idea of their data being on the same physical server as that of other companies, although virtualization technologies make those arrangements generally more efficient.

Microsoft's moves toward cloud computing have come as the company repeatedly emphasizes that it doesn't see those services replacing on-premise software, or applications installed on PCs.

Other companies, such as Microsoft's competitor Google, have been strong proponents of Web-based applications accessed through a Web browser, which can be cheaper and updated instantly but are dependent on reliable Internet connectivity.

"We believe people will continue to want to run software on premise," Clayton said.