Facing what he called "universal truths about product development," Microsoft general manager for virtualization strategy Mike Neil concluded a multi-page blog post this afternoon touting the progress made with Windows Server Virtualization, code-named "Viridian," by announcing the removal of three of the service's most highly anticipated features: live migration of running virtual machines between servers; "hot-adds" of virtual components such as storage, processors, and memory; and support for more than 16 logical processing cores.

"With all this progress comes the occasional tradeoff," Neil wrote this afternoon. "Earlier this week we had to come to grips with some universal truths about product development: *) Shipping is a feature, too; *) The quality bar, the time you have, and the feature set are directly correlated."

While last month's delay was explained as having been necessary to enable these features to be fully developed, Neil today explained the cuts as necessary in order to ship the product on time.

In last month's explanation of Viridian's delay until the second half of the year, he wrote, "Why the schedule change to the beta of Windows Server virtualization? The primary drivers are around meeting our internal goals for performance and scalability. In an IT environment of ever-growing multi-core processor systems, Windows Server virtualization is being designed to scale across a much broader range of systems than the competition. We're designing Windows Server virtualization to scale up to 64 processors, which I'm proud to say is something no other vendor's product supports. We are also providing a much more dynamic VM environment with hot-add of processors, memory, disk and networking as well a greater scalability with more SMP support and memory."

Contrast that statement with Neil's post this afternoon, which states his team made a strategic decision to focus on what customers really need, which led to excising the excess scalability.

"We adjusted the feature set of Windows Server virtualization so that we can deliver a compelling solution for core virtualization scenarios while holding true to desired timelines," Neil wrote today. "Windows Server virtualization is a core OS technology for the future, and we chose to focus on virtualization scenarios that meet the demands of the broad market - enterprise, large organizations, and mid-market customers."

Neil did make clear, however, that the first public beta of Viridian will be made available in the second half of 2007, in keeping with the release-to-manufacturing for Windows Server "Longhorn," and that a production edition would be available within 180 days after that. However, Microsoft spokespersons decline to acknowledge that Longhorn's RTM date will be in the second half of the year, despite statements that the Viridian beta will be released in the second half of the year.

The removal of these features comes just days before the start of Microsoft's WinHEC conference in Los Angeles. There, several demos remain on the schedule, including public demos of the very features Microsoft has chosen to cut. Neil said today the company still plans to include these features in a future Windows Server Virtualization release, though the code-name "Viridian" was not used in that sentence.

What would these features have actually provided that's so important? Architects of large enterprise networks are looking for ways to simplify their logical structure. Just because they end up using multiple processors distributed geographically in far-flung locations, should not mean they have to build complex domains and, in Windows terminology, forests of domains just to make everything work together.

A virtual server environment would enable a broad array of processors to function jointly as a single entity from a logical perspective, simplifying the job of managing applications and functions enormously. But for large networks, this may only be feasible if the virtual entity can scale among a large number of processors, and do so "on the fly," whenever it needs to.

A 16 logical processor limitation will restrict a Viridian virtual server to only four quad-core processors, which could effectively box it in within a 4P server. What's more, if you can't add processors and memory on the fly, as they become available, you can't subtract them either, which will probably mean that for virtual servers distributed across multiple physical processors, little can be done to rescue the VM if one processor goes down.

One feature that apparently will remain in Viridian is the "snapshot" feature, which enables a virtual server to be backed up in its entirety, and reverted to if an experiment or other circumstance causes the virtual server to be unusable. 64-bit VMs will also continue to be supported.

5:09 pm May 10, 2007 - After reading this story, a Microsoft spokesperson officially reversed repeated declines by the company to officially set a timeframe for Longhorn's release to manufacturing - despite apparent references to it as a relative milestone for other products and services such as Viridian - by saying indeed, Longhorn will RTM in the second half of 2007.

The RTM date has also appeared incidentally in recent press releases, the spokesperson reminded us.