For now, however, Unix systems are still very much in the mix as Marriott plans migrations on a case-by-case basis. "We do not have a strategy to just close our eyes and go with one particular platform to the exclusion of all others," he says. Qualcomm is also getting more bang from the buck from its Solaris 10 systems by taking advantage of the operating system's virtualization technology, Solaris Containers. That feature was also responsible for stopping the Linux transition plans at Bank of New York Mellon in its tracks.

Dennis Smith, first vice president in the bank's advanced engineering group, says that when he started planning last January, he anticipated a wholesale "replatforming" of all of the Solaris systems at the bank onto Linux servers. That hasn't happened. After transitioning a few systems, Smith decided to bring Sun back in to talk about leveraging its virtualization technology and began to experiment with Solaris Containers. "We're in the middle of that now," he says.

Sun's Containers technology, which creates virtual machine instances that share a single copy of the operating system, can make for a compelling economy of scale argument, Iams says. It can scale much better than , it is more mature than Parallels' Virtuozzo and it's supported by Sun as part of the core operating system. With Containers, he says, "You have a much smaller footprint per instance so you get a much higher level of consolidation. While you might a few dozen [virtual machines per physical server] with VMware, with Containers it's hundreds -- or even thousands -- per server." Smith saw enough of a benefit from Containers to change his plans -- but he's still keeping Linux in the picture. "We won't be as aggressive in replatforming to Linux as we initially thought," he says. But, he adds, "We feel that both platforms will have a place in our infrastructure."