Linux has grown rapidly over the last several years, moving from Web operations on the perimeter of the enterprise to workloads much closer to the heart of the business. In the process, it's gained a broader following of contributors and commercial users.
At the same time, the easy part of Linux's advance may be over. IDC analyst Al Gillen told about 300 attendees at the Linux Foundation Collaboration Summit in Austin, Texas, Tuesday that Linux has made many of its gains at the expense of legacy Unix systems. From here on, its growth may slow, as result of both server virtualization, which packs more applications on a single server, and head-to-head competition with Microsoft's Windows Server. "Never discount Microsoft," added Gillen.
Sun Microsystems stemmed Solaris users' erosion to Linux when it made its operating system open source code, said Gillen. "Solaris is not necessarily a threat, but it's going to be a competitor," said Gillen, in his keynote address.
Linux is more and more frequently acting as a database server, growth "that's heavily driven by Oracle," Gillen said. At the same time, Linux is assuming more business application workloads, including enterprise resource planning, customer-relationship management, and financial applications. "By 2011, the logistics and manufacturing applications alone will be a $1.2 billion market on Linux; human capital management will be a $2 billion market," he predicted.
Gillen has been tracking Linux since the first IDC Linux marketplace study in 1999. By 2011, the market for Linux systems -- server hardware plus operating systems -- will amount to $50 billion. Windows will still lead Linux by a wide margin. A way of comparing the two, he said, is Linux and Unix business applications together will amount to $96 billion in 2011 (with Linux applications representing one-third of the total); Windows Server applications, $110 billion.
But Gillen cited additional figures that show for every supported copy of Linux running in the enterprise, there is another copy running unsupported and unpaid for. The Linux ecosystem is twice as large as it appears in IDC revenue data because so many users feel they have the skills in-house to support their Linux system or are willing to rely on support from Linux community members.
Gillen's analysis was part of the second annual meeting on the status of Linux sponsored by the foundation. It is a nonprofit group headquartered in San Francisco, whose corporate sponsors include Oracle, HP, IBM, and its most recent recruit, Adobe Systems.
Part of the purpose of the summit is to let business users see and interact with Linux kernel developers, who are sometimes distant, god-like figures with absolute power over the operating system's core. One person glad to have the opportunity was Ed Reaves, a Nortel technology platform manager from Research Triangle Park, N.C.
Linux end users and server administrators are happy with 99.999% of uptime, Reaves noted, but Nortel and other telecommunications companies would like to move Linux reliability to 99.9999%, or one outage of about 30 seconds per year. Nortel's Linux developers produced a block of code that restarts Linux in 20 seconds in the event of a stalled operating system, called "the restart instead of halt patch," he noted.
But it doesn't appear to be moving into the kernel, to the dismay of Nortel executives concerned about avoiding outages. "How do you get a kernel patch released into the mainline?" Reaves asked, referring to the development process that steers additions to the kernel past reviewers and into a hierarchical code tree maintained by Linus Torvalds.
Kernel development is a many-segmented process, with key developers responsible for particular Linux subsystems. "The limiting resource is not development of code but review of code," responded Jonathan Corbet, a kernel developer and author of the Linux Foundation's "Linux Forecast" published on its Web site.
The smaller the patch, the more likely it is to find a speedy review, he added. The Nortel patch, however, was a sizable block of code requiring someone with knowledge of a particular part of the kernel.
James Bottomley, the kernel developer responsible for the SCSI subsystem, added, "It's necessary to find the right kind of review." The reviewer needs to have expertise in the area of the submitted code, time to review, and the respect and trust of the kernel maintainers in his subsystem area. The reviewing process is less recognized than the code writing, which has prompted kernel developers to include a "reviewed by" tag with patches to acknowledge the role of the reviewer.
"The bar is just high," conceded Arjen van der Ven, a kernel developer employed by Intel who works on Linux power management.