Microsoft is to change the initial service pack of bug fixes and enhancements that had been planned for its Virtual Server 2005 software into an "R2" product upgrade that some users may have to buy.

There have been no major feature changes since Microsoft announced a beta version of what was supposed to be Service Pack 1 for Virtual Server 2005 in April, said a company spokesman. But Microsoft officials decided that the update's performance and availability improvements, 64-bit compatibility and other planned enhancements "passed the bar" necessary for a full product release, said Zane Adam, a director of marketing for Windows Server.

Users who bought a Software Assurance maintenance package for the virtualisation software as part of a volume licensing deal with Microsoft will be able to get the R2 upgrade for no extra cost, Adam noted. But those who didn't purchase the maintenance plan will have to pay for R2.

"It would probably be a significant issue for us if we had deployed [Virtual Server] in more areas and we didn't have Software Assurance," said Michael Brown, a support services manager at the Denver Health and Hospitals Authority. "This is certainly different from Microsoft's traditional model."

Microsoft users are accustomed to getting a service pack update following the release of an enterprise product, Brown added. He said Denver Health will test the R2 upgrade when the final version is released later this year.

Like Denver Health, four other users contacted by Computerworld said they purchased Software Assurance packages for Virtual Server, which allows multiple copies of an operating system to be run on a single computer.

"Usually, if we're going to use something long term, we buy it with Software Assurance," said Stan Johnson, a desktop and LAN services manager for the Multnomah County government in Portland, Ore. "So the fact that they're doing a new product release isn't a significant concern to me."

Beyond a service pack
Demond Hatter, a technical analyst at Exelon Corp. in Chicago, said he typically considers a service pack to be oriented toward bug fixes. "If this is more of a functionality enhancement, I can see it not being a service pack," he said.

Virtual Server users who lack Software Assurance's upgrade protection won't miss out on critical bug or security fixes, according to Adam. However, they won't get the rollup of fixes that comes with a typical security pack unless they opt to buy R2.

Microsoft "sweated" over the decision to make R2 a product release, Adam said. But, he added, the company was in a somewhat unique situation with Virtual Server, since it has been on the market only since last October.

Adam said Microsoft studied the Virtual Server customer base and found that the majority of users with multiple copies of the software have Software Assurance as part of volume licensing contracts.

Microsoft provided an update on its virtualisation plans at last week's Intel Developer Forum in San Francisco. The software vendor's long-term virtualization road map calls for a thin, hypervisor layer of code supporting virtualisation capabilities to be built into the next major release of Windows Server, code-named Longhorn. But Microsoft has said that the hypervisor technology won't make it into the initial Longhorn server release due sometime in 2007.

In the interim, Microsoft intends to develop a second full version of Virtual Server that will follow the R2 release. Last week, it outlined plans to ship a beta copy of that version in the first half of 2006 and the finished software in the second half of the year.

The promised new features include support for Intel's performance-boosting virtualisation technology, VT, as well as AMD's rival Pacifica approach.