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If you're a techie entrepreneur creating a big e-commerce site, you may decide to buy a high-end Unix box to accommodate the volume and processing demands your bean-counters have projected for you. You'd run Sun Microsystem's Solaris software on it to power your Web server and e-commerce applications.

Or, you could opt to save a little venture capital and run Linus Torvalds' free operating system (and its accompanying free server apps) on a cluster of commodity Intel PCs.

The Linux OS is well-suited to small- to medium-sized operations, and is increasingly being used in large enterprises that would have previously considered Unix the only option. It has taken hold in Internet and e-commerce businesses, making the decision on whether to use Unix or Linux not as cut-and-dried as it may seem. A few years ago, the decision on whether to implement Unix or Linux was a no-brainer. Linux was an interesting academic project, but most people didn't consider it an option for a serious, commercial enterprise. How can it be that good if it's free? Isn't it just a toy for hackers and college students? But the maxim "you get what you pay for" doesn't really apply in the open-source world.

With major software vendors porting their applications to Linux, the OS has entered the mainstream as a viable option for Web serving and office applications and as a growing force in e-business (see Penguins running wild.)

Linux or Unix?

So when do you use Linux, and when do you use Unix? There are indeed some circumstances where Unix is the obvious choice, and Linux just won't do. "If you are talking about very large, massively symmetric multiprocessing systems, systems with greater than eight CPUs, you do need a full-blown Unix," says Jeremy Allison, Samba Team Lead at Fremont, Calif.-based VA Linux Systems. The current Linux 2.2 kernel does not scale well past four CPUs in a multiprocessing environment, but Allison says that the 2.4 kernel will scale significantly better--up to at least 16 CPUs. The 2.4 kernel, currently in beta, is due for final release in the first quarter of 2001.

Allison adds that a proprietary Unix system is probably better suited to a massive, single-box data center. "But there aren't that many applications that actually need something that large," he says. Moreover, many applications that do require mega-processing power can achieve that power through clustering, which both Unix and Linux do very well. The open-source project Beowulf has spawned a technology that links cheap PCs running Linux, creating the equivalent of a parallel supercomputer capable of process-intensive tasks such as rendering special effects in movies, climate modeling, or data mining.

Projects like Beowulf have made Linux one of the most scalable OSs. "There are versions of Linux that you run on PDAs, and there are versions which run on IBM mainframe computers," says Paul McNamara, vice president of products and platforms at Red Hat, Inc. of Research Triangle Park, NC. "We're seeing a wide variety of customers deploying Linux on large-scale, mission-critical applications."

Linux has the obvious upper hand with the budget-conscious; it's hard to compete with free. Since Linux involves no licensing fees, you can buy one copy of the OS and install it on as many machines as you want. Commercial Linux Web serving applications also tend to be less expensive than their Unix equivalents, because of unified standards in the open source model. Because software companies have to create a separate port for each different flavor (Solaris, AIX, A/UX) of Unix, those applications carry much heftier price tags much higher than those written for Windows 2000 or Linux. "One of the real advantages of Linux is that it ships with all these server applications already installed," Allison says.

File and print serving, Web serving, database management and a host of other applications come bundled with the base system, making it very cost-effective to use. Neither Unix nor Linux is that difficult to use anymore, and both have standard GUIs similar to that of Windows 2000. Allison, however, gives the nod to Linux when it comes to usability. The OS is "incredibly easy to use," he says, noting that