While recent research from Gartner Dataquest shows that Linux server sales are up compared to Unix boxes, that's not the whole story when considering how much Linux is actually being used in enterprise networks.
Many vendors sell Linux servers preconfigured, but it is still not uncommon for savvy IT departments to build their own servers with Linux. And more often than not, it's a Windows-based server that's being blown away when Linux is installed on the hardware.
"I've bought plenty of servers from [major brand name] companies and wiped the drives clean in order to install Linux," says Jeff Davis, a systems programmer who works with a cluster of 320 Linux boxes at the oil company Amerada Hess in Houston.
This helps put recent Linux server sales numbers more in perspective. According to Gartner, Linux servers accounted for 4% of worldwide sales of all servers in 2002.
Another Linux user also pointed out to me that there's more to the Linux usage story than the server sales statistics would suggest. This user's company spent in the low six figures on server hardware that's actually being used to run Linux but shows up on the books as Windows server revenue.
"The servers are from Dell and came with licenses for Windows, and Dell seems to have no record of the fact that they are used for Linux," the user says, adding that when he has called Dell, customer service representatives have asked "Which version of Windows are you running?"
"I expect the number of servers purchased for running Linux to be at least twice the number of servers that had it preloaded," this user adds.
While sales of servers shipped with Linux accounted for around 4% of all servers, another researcher, IDC estimates that Linux is the second-most shipped boxed operating system software after Microsoft Windows.
If you also consider that that open-source licensing allows users to (legally) install a single Linux server copy onto multiple machines, the amount of Linux usage vs. Linux server revenue could be even more disparate.
"That's one of the nice things about Linux," says Amerada Hess's David. "You can put one copy on more than one machine, which can keep the cost down."