Commercial enterprise UNIX today reminds me of vintage clothes and furniture.Just when you think certain things have become pass\u00e9 in favor of newer more modern things, they are somehow revived and come back into fashion.For the 11 years that I've been writing about enterprise IT, every once in a while a new rumor or expert opinion would surface declaring that UNIX was finally dead due to (take your choice) cheap x86 hardware, the continuing development of Linux for the enterprise or even due to the broadening power and features of Microsoft's Windows operating systems.Yet despite the fact that the alleged decline of UNIX keeps coming up, it's still breathing. It's still widely used in enterprise data centers. It's still running huge, complex, key applications for companies that absolutely, positively need those apps to run.And despite the ongoing rumors of its imminent death, its use is still growing, according to new research from Gabriel Consulting Group Inc.So what's going on with UNIX in the summer of 2011?"We believe and always have believed that the UNIX market is important, although it doesn't get the attention" of other technologies, says Dan Olds, principal analyst with Gabriel Consulting. "This is a large market and it's not something that will go away anytime soon."For the last five years, Olds has been conducting annual surveys on enterprise UNIX usage and the data doesn't lie, he says. "Some people in the industry think that commercial UNIX isn't relevant anymore, but look at what I'm finding out from those who are using it."Out of 306 enterprise IT respondent s in the latest study, released in June, 89 percent agreed that UNIX systems are strategic in their IT systems, according to Olds. Those figures, representing the fourth quarter of 2010 through the first quarter of 2011, compare with 91 percent for the same period one year ago.And out of those 306 users, a combined 52 percent say that at least 75 percent of those UNIX workloads are mission critical to their businesses, according to the data. Another 26 percent say that at least half of their UNIX workloads are mission critical. That's a lot of satisfied, confident users, Olds says."Those users are saying 'we have to have it,'" Olds says. "And it's not surprising. What's happened in the past decade is that when technology really took off in the 1990s, UNIX systems were really the only game in town" for enterprise users. "It was the only operating system that was Web-enabled and that could be scalable and powerful enough to do what businesses needed to do."Then came more progress and choices in the world of computer operating systems, he says."What changed is that Microsoft Windows and Linux got a lot better and a lot more stable and x86 systems got better" for use by businesses. "They became the 'good enough' and low-cost alternatives to get things done."Slideshow: The Oddest Places to Find LinuxThe thing is, though, that while many of those x86 systems today run a lot of the same applications as the mission-critical UNIX systems have always run, "there are still some things that commercial UNIX does that they just can't match," Olds says. That includes things like vertical scalability and high-availability for systems and workloads.The key reasons that UNIX is still surviving and thriving, he says, is because it's still needed for the critical apps that huge enterprises depend on, including ERP, CRM, BI and more. "What's happened with UNIX over the years is that it's become that 'go to' machine when you need predictable performance and high-availability. That's become the UNIX niche," he says. "These respondents are running these kinds of workloads. For this reason alone it's likely that UNIX will continue to exist for a long time."In the meantime, there's no dearth of UNIX vendors, either, even with all the consolidation in the industry over the last 20 years or so.The main players continue to be IBM, Hewlett-Packard and Oracle (with its Sun Solaris offering). "With three competitors left standing, it will remain competitive," Old says."In the real world, when you have to get things done, there's a market for everything," he says, and that's another reason UNIX is still around and popular. "In the right places, it's still the most efficient, most highly-available and lowest cost solution out there."And these are not tiny, unimportant users who were surveyed, Olds says. "These are people who have big infrastructures. They know what works." At least 44 percent of the respondents have more than 10,000 employees each, while another 33 percent have less than 1,000 employees per company. "The sweet spot for UNIX is typically bigger organizations. That's where UNIX fits."Gabriel Consulting's research also found that of their 306 respondents, about 45 percent say that they would be increasing their UNIX usage from late 2010 to early 2011. At the same time, brand loyalty isn't a big factor, with 45 percent of the respondents saying they use combinations of UNIX from at least three different vendors.The brand diversity might be a result of enterprises having "different needs in their data centers," Olds says. It also could be due to good deals from vendors over the years that caused them to diversify their use of various UNIXes.So where does Linux fit in all of this? Has Linux been replacing UNIX in enterprise data centers in a big way?Well, according to the Gabriel research, while Linux is certainly well-regarded in corporate data centers and has a large footprint, UNIX still maintains its long-held reputation as the operating system of choice for enterprises that need to run mission-critical systems and workloads, at least with the 306 respondents to the studies.Twenty-nine percent of the respondents say that they agree that UNIX is ahead of Linux in many key ways, with another 28 percent saying they strongly agree, for a total of 57 percent. Twelve percent strongly disagree, while another 15 percent disagree with that statement."The thing is that Linux has a really vital and important place in the enterprise, but still not as big a mission-critical part in the data center," Olds says. "Most of the applications that are out there right now, they run on Linux, but what you don't get are these systems that vertically scale. For a main enterprise SAP database application, you're not going to play around with that" and try to run it on Windows or Linux.Asked if they think that Linux is technically superior today to UNIX, 17 percent of the respondents say they strongly disagree, while another 42 percent disagree, according to the study. And 56 percent say that they agree or strongly agree that UNIX is more available and reliable than Linux. That's not a big majority, but it shows these UNIX users may be a dedicated lot.What about the number of UNIX users that might be migrating to Linux?A combined total of 65 percent say they won't migrate to Linux within the next five years, while 17 percent say they will make that move. A combined 75 percent say that they'll stick with UNIX for the long-term future, at least for the next five years.So what's this all mean?As I've covered Linux and UNIX over the years, I've heard many times as users and vendors would discuss how Linux was replacing or would replace UNIX in enterprise IT from top to bottom.We still hear these arguments today.Of course, we sometimes also still hear that this is really going to be the year when Linux finally makes it to the enterprise desktop. But that still hasn't happened yet either.It leads me to believe that Olds is right in his viewpoints and that he has the best philosophy here.Yes, all these different operating systems options exist for all the different workloads in IT so that users can choose what they want and need. That's why UNIX is still here, because it's still doing its job for the enterprises that love it and trust it. And Linux is there for others, and Windows and whatever for everyone else.That's the way it's supposed to be in IT. You pick your vendors, your operating systems, the brands you like, the software that will best do the job and then you head out and do your work and make your company's IT systems hum.So is UNIX dead?Nope, not by a long shot.I'd love to hear your thoughts and experiences. Is UNIX still a key operating system in your enterprise? Is it still running your mission-critical applications? Are there plans for a Linux or other migration?Tell me your stories and I will share them with our readers.What do you think about UNIX in your enterprise in 2011?