• Illustration: New Virtualization Schedule

Key features in the planned Windows Server virtualization service (code-named Viridian) will be cut from the initial release in order to ship within 180 days of the release of Windows Server 2008 (formerly code-named Longhorn). The announcement means that customers might have to turn to competitive virtualization technologies to get key features that Microsoft will not deliver for a year or more. Also delayed to the second quarter of 2007 is Virtual Server 2005 R2 SP1, which will exploit new processor features to improve virtualization performance.

The changes were announced in a carefully worded blog entry which appeared just before the start of the 2007 Windows Hardware Engineering Conference (WinHEC). Microsoft likely wanted to get the bad news out of the way so that it would not overshadow the company's WinHEC announcements.

Viridian Cut for First Release

Virtualization technology allows multiple, different OSs to run simultaneously on a single device—each OS runs in its own virtual machine (VM, or computer created in software) on the hardware of a single physical computer. In 2004, Microsoft decided to make virtualization an integral capability of the Windows OS rather than letting it remain a separate product. Furthermore, while Microsoft undoubtedly had learned a great deal from its Connectix acquisition, from which it gained Virtual PC and Virtual Server, it decided not to use the Virtual Server architecture and code base it inherited from Connectix but to instead start over with a clean slate for the virtualization services included in Windows.

At the core of the new Windows virtualization architecture is a component called the Windows hypervisor that sits at the lowest level of the host OS and abstracts and controls access to hardware for multiple guest OSs running in VMs.

Microsoft has committed to making the new architecture backward compatible with VMs for older Virtual Server versions, so migration of existing Virtual Hard Disk (VHD) files to a new Longhorn Server should be relatively painless.

Delayed Features

The features pushed back to a future release of Windows Server virtualization include the following:

• Live migration, an important and highly touted feature that allows administrators to move running VMs between servers without disrupting services to clients
• Hot-add of virtual resources, which allows administrators to add storage, network cards, memory, and processor hardware to a running system
• Support for more than 16 cores or logical processors; while systems with more than 16 CPU cores are rare today, they will be more common when Viridian ships, and this limitation could affect the ability to use the virtualization service on hardware with more than 16 cores to handle large consolidated server loads.

Virtual Server 2005 R2 SP1 Delayed

Microsoft has also delayed the release of SP1 for its existing Virtual Server 2005 R2 product. SP1 has been in beta for a year and is now planned for release by the end of the second quarter of 2007. In addition to bug fixes, SP1 will exploit AMD Pacifica and Intel VT hardware, which should substantially improve performance for non-Windows guest OSs. SP1 will also allow host snapshots of the VHD files of running VMs, which will make VM backups and rollbacks easier. Although SP1 will not require Windows Server 2008, it will support Windows Server 2008 as both a host OS and a guest OS.

System Center Virtual Machine Manager 2008 R2, a management product that will support both Virtual Server and Viridian, will be available 60 to 90 days after the public beta release of Viridian for customers to test deployment and migrations.

Cut Gets Project Back on Schedule?

Microsoft seems confident that the feature cuts and delays will put Viridian back on schedule. (For a visual representation of the schedule, see "New Virtualization Schedule".)

The beta release of Viridian will allow customers and partners to test workloads and applications on a preproduction version of Windows Server virtualization with the final version of Windows Server 2008. However, given the time necessary to gather feedback and resolve reported bugs, six months between release candidate and release to manufacturing remains a very optimistic schedule. Furthermore, the company has not said how it will release Viridian when it is complete—for example, as a service pack, feature pack, or part of some other package. There are also few details as to when the features that it has cut will appear, except that they will be in "a future release of Windows Server virtualization." That will likely not happen before 2009.

Resources

Microsoft's virtualization technologies, products, and strategies are detailed in "Changes to Server Virtualization Roadmap" on page 14 of the Jan. 2006 Update and "Virtual Server Free, Linux Guests Supported" on page 5 of the June 2006 Update.

Microsoft's virtualization technology is described at www.microsoft.com/windowsserversystem/virtualization/default.mspx.

A blog entry on the latest virtualization changes is at blogs.technet.com/windowsserver/archive/2007/05/10/viridian-features-update-beta-planned-for-longhorn-rtm.aspx.