As Red Hat Inc. prepares to launch the Red Hat Enterprise Linux 5 operating system on Wednesday, the question is again being asked whether a robust and feature-laden operating system is really needed for some computing situations.

Makers of "software appliances" are using the launch as an opportunity to predict that the days of the monolithic OS are numbered. They say the future lies in a modular system in which software runs with only enough lines of OS code to make it work.

Some see promise in the appliance alternative to the OS, while skeptics think large enterprises will still need a general-purpose OS.

The same questions arose recently around the launch of Microsoft Corp. Windows Vista. A trio of Gartner Inc. analysts published a report in 2006 that said the increasing complexity of Windows makes it "unsustainable." Gartner predicted Windows will be broken up into modular components.

The same could be said for Red Hat Enterprise Linux 5 (RHEL 5), said Billy Marshall, CEO and cofounder of rPath Inc., a software appliance platform vendor.

As new features are added to it, RHEL 5 has become just as unwieldy as Windows, Marshall said. "It's bigger and more bloated."

OS vendors add all sorts of functionality in the event some enterprise may want it, and the addition of these features is one of the reasons why both Microsoft and Red Hat have encountered delays bringing their products to market, he said.

Installing an OS could use as much as 1.82G bytes of space on a hard drive, he said. A software appliance with only the code to run one application would use just 300M bytes, he said.

"The general-purpose OS model is breaking," Marshall said.

Another software appliance vendor, Ingres Corp., on Feb. 27 launched a database management software appliance it calls "Icebreaker" to compete against IBM Corp.'s DB2 and Oracle Corp.'s database software.

Software appliances may have a place in some niche environments in which a customer needs to run just a few pieces of software, said Jay Lyman, an analyst with The 451 Group. But a larger business would probably still need the various programs that are bundled into an OS, he said.

It might be possible to run an enterprise infrastructure without an OS, Lyman said. "But then again, you've already got people [in your IT department] running the OS, and it's a pretty critical part of the infrastructure."

The IDG News Service is a Network World affiliate.