IT managers who once used Linux chiefly to support Web and file-and-print servers said at last week's LinuxWorld Conference & Expo here that they're now running key applications and databases on Linux-based systems -- a sign that the open-source software is penetrating deeper into corporate enterprises.

"It's as deep as it will get for us. It's what we're betting the data centre on," said Jon Fraley, a Linux administrator at textile manufacturer Glen Raven. In December, the company finished moving mission-critical Oracle databases from an aging 24-CPU HP server running Unix to four-way Xeon servers from HP running Red Hat Linux.

Reports that once took five to six minutes to produce are now ready in 30 seconds, Fraley said. He noted that the replacement servers cost less than the support fees for the old hardware. The Linux-based hardware "proved itself," he said, adding that more Linux servers are on the way for a disaster recovery site.

New enterprise Linux capabilities are also helping early adopters such as Yahoo venture into new terrain. Yahoo already had "lots" of Linux servers running Yahoo services, databases, business intelligence software and reporting applications, said Mason Ng, Yahoo's director of engineering operations. He declined to provide the specific number.

But in December, Yahoo started to port its home-grown infrastructure applications from its custom operating system to Red Hat Enterprise Linux 4.0, which was in beta at the time and was released last week. Plans call for a gradual migration of more applications to Linux, but the timing and number will depend on how successfully the early work goes, Ng said.

He said the performance improvements and 64-bit support in the Linux 2.6 kernel fuelled the decision to considering porting some of the applications. "From a performance and scalability standpoint, earlier versions of the kernel couldn't meet our requirements without heavy customisation," he said.

Yahoo also expects to run more databases on Linux. Ng said the company currently has dozens of database instances on Linux, and he expects the number to double in the next 12 months. Yahoo isn't running any 64-bit databases in production on Linux yet, but it is testing them, Ng added.

Continental Airlines began pushing the 64-bit database envelope last September when it went live with an automated ticket-reissue application. The system uses MySQL AB's open-source databases running on three four-processor HP DL585 servers. The open-source software stack also includes JBoss's application server and the Apache Web server.

Michael McDonald, director of technology at Continental, said the Houston-based airline gained confidence in Linux after seeing continuous uptime of as much as 300 days while running it on development machines. Security patches could be applied and applications installed without bringing the system down or rebooting. "We thought from a reliability perspective that the operating system was ready," McDonald said.

The new application replaced a manual process that took as long as 20 minutes for a ticket agent to complete. Customers are now able to get answers in seconds, McDonald said. The project has been so successful that Continental will consider Linux as it looks to partition its mainframe into subsystems and move some of the subsystems to distributed servers, he added. The mainframe runs IBM's Transaction Processing Facility software.

IDC analyst Al Gillen said the first wave of Linux adoption focused on Web servers, network infrastructure and file-and-print servers. But users are now "well into the second wave" of adoption for uses such as database servers, collaborative software and application workloads, he added. A third wave, which is "arguably beginning," focuses on server virtualisation and provisioning of on-demand computing, Gillen said.