Experts say that migrations from Unix to Linux have slowed down because all the low-hanging fruit has now been picked.
Linux growth in the U.S. x86 server market has, over the past six quarters, started to falter and reverse its positive course relative to Windows Server and the market as a whole.
The annual rate at which Linux is growing in the x86 server space has fallen from around 53 percent in 2003, when Windows Server growth was in the mid-20 percent range, to a negative 4 percent growth in calendar year 2006, IDC Quarterly Server Tracker figures show.
Over the same time period, Windows has continued to report positive annual growth, outpacing the total growth rate in the x86 market by more than 4 percent in 2006, indicating that Linux has actually lost market share to Windows Server over this time.
The same holds true for worldwide Linux x86 server shipments, which dropped from the huge annual growth rate of about 45 percent is 2003 to growth of less than 10 percent in 2006, the IDC figures show.
One of the biggest reasons for this is that the migrations from Unix to Linux have slowed down markedly.
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"We have seen the rate of migration from Unix slow over the past few quarters," IDC analyst Matt Eastwood told eWEEK. "In my view this is because much of the low-hanging fruit has been moved and the applications that remain on Unix are stickier because they are seen as business critical and more political candidates for migration overall."
IDC analyst Al Gillen pointed out that the number of servers shipped does not perfectly equal the number of operating systems in the market. This is particularly the case with Linux where a substantial portion of the overall market opportunity comes from deployments aboard recycled servers, PCs and workstations deployed as servers, and Linux deployed as a guest operating system.
"This does not contradict any trending taking place on server hardware," Gillen said.
He added: "But we do need to remember that the Linux software ecosystem does not track exactly the same as does x86 hardware shipments."
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Margaret Lewis, the director of commercial solutions for AMD in Austin, Texas, has also noticed the slowdown in Linux growth over the past few quarters.
In 2000, Windows comprised about half of the server operating system market, followed by Unix and Netware at about 17 percent each and Linux reaching towards 10 percent, she said, noting that today Windows owns about 70 percent, Linux about 20 percent, with Unix below 10 percent and Netware barely registering.
"Looking at these large operating system market swings, you could draw the conclusion that Linux has gotten the low-hanging fruit in terms of migration," Lewis said.
"Without the larger pool of Unix and NetWare users who are ripe for migration, there is not quite the level of fuel. You could assume that Linux is now ready to settle down to a more regular growth curve representative of a more mature technology."
The fact that Windows has maintained a steady growth rate over this same time frame could be the result of companies expanding their Windows-based IT infrastructure to meet the demands of users who always want to be online, she said.
"Windows-based Web hosting sites are experiencing strong growth, the Exchange infrastructure is expanding to offer unified messaging and many small businesses are moving to a real server infrastructure for basic infrastructure instead of a network of desktops," Lewis said.
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Bill Hilf, general manager of Windows Server marketing and platform strategy at Microsoft in Redmond, Wash., has also noticed these trends, and says that increased customer adoption of Windows Server 2003 in a broad range of enterprise scenarios is driving significant growth of that business.
"I spend a lot of time talking with both Linux and Windows customers and partners, and the feedback that I hear is that, in volume, Linux is primarily deployed in two workloads—high-performance computing and as Web servers," Hilf told eWEEK.
"It appears that Linux server growth is moderating considerably and, while its certainly still a player, its not being considered across the broad range of workloads that Windows Server is, from ERP to CRM to messaging and collaboration to core infrastructure like file and print," he said.
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