Microsoft is expanding its "Get the Facts" campaign against Linux by talking about the reliability of Windows versus Linux systems.

Get the Facts is a marketing effort by Microsoft that compares Windows favourably with Linux and other open source software products. The campaign was launched in mid-2003 and has gradually expanded its scope to now include issues such as total cost of ownership, security, indemnification, and now reliability.

"Reliability has been challenging for us. It is an area that has been very noisy," says Martin Taylor, general manager of platform strategy at Microsoft. "Customers say that reliability is very important to them and that they are hearing that Linux and Unix are more reliable than Windows."

In the absence of a clear definition of reliability or benchmarks, Microsoft commissioned a study that pitted Windows Server 2003 against Red Hat Enterprise Linux 3.0 AS. As part of the study, 18 Linux and 18 Windows system administrators were hired to run the simulated IT environments of a midsized company over a four-day period.

The administrators had to troubleshoot intentionally introduced errors and conduct tasks such as configuring new devices, making backups and setting up remote access.

"We found that the Linux environment provided about 15 percent more loss of productivity," Taylor says. Over the 26 hour test period spread over four days, the Red Hat systems had services down for 4 hours, 59 minutes and 44 seconds, while the Windows system had users waiting for services for 4 hours, 20 minutes and 19 seconds, according to a copy of the study, which was conducted by VeriTest.

The Windows administrators were able to complete more assigned tasks, troubleshooting was easier on Windows and Windows administrators needed 33 percent less in average total time to do their tasks than on the Linux side, the study says.

But open source advocate Bruce Perens disputes the notion that Windows is more reliable than Linux and gives a simple example: computer viruses.

"Look at the viruses. Every day my mailbox gets 30 Windows viruses in it. They come from systems that have already been infected and are just sending out viruses to everyone they know. And that is not happening to the same extent for Linux or open source software," he says.

According to Perens, open source software will always be less prone to virus attacks because it was designed to be connected to the Internet. "Microsoft is still catching up with that," he says.

Having compared "apples to apples," Microsoft's Taylor says that he feels good about Microsoft's reliability story.

However, in real life Windows and Linux are not used for the same type of tasks, according to an independent Yankee Group survey of 509 IT users released earlier this week. The hourly cost of Windows downtime in actual user environments is three to four times higher than that of Linux downtime, according to Yankee Group.

Windows downtime is more expensive because the operating system is used for more crucial tasks in businesses when compared with Linux servers, according to the Yankee Group survey. Users also told the researchers that Windows and Linux security are nearly equal and that Windows recovers 30 percent faster from attacks than Linux servers.

Furthermore, according to Yankee Group, Linux is not displacing Windows in server rooms, but most users are installing Linux servers parallel with Windows servers.

Microsoft plans to use the reliability data it got from the VeriTest study in new advertisements, Taylor says.

Robert McMillan of the IDG News Service contributed to this report.