Executive Summary:
Windows Server Virtualization, code-named Viridian, will be available as an add-on to Windows Server 2008 (formerly code-named Longhorn). Windows Server Virtualization combined with Windows Server 2008 lets you create virtual machines (VMs) that feature great scalability and high availability.

Virtualization is one of today's fastest-changing technologies, and nowhere is that more evident than in Microsoft's new product, Windows Server Virtualization (code-named Viridian), which will be available as part of Windows Server 2008 (formerly code-named Longhorn). Microsoft is promising to deliver the release to manufacturing version of Windows Server Virtualization within 180 days of the release of Windows 2008. (A prerelease version of Viridian will be included with the initial shipping version of Windows 2008.) Here are some of the coolest features you can expect from Microsoft's next wave of virtualization technology.

10. New Windows-based management console—The first thing you'll notice is the modernized management console. The new console, based on Microsoft Management Console 3.0, includes wizards for creating virtual machines (VMs) and a task pane for performing management functions.

9. Standard VHD image—Windows Server Virtualization supports Microsoft's Virtual Hard Disk (VHD) format, so you can use VM images from Microsoft Virtual Server 2005 and Microsoft Virtual PC with the new product.

8. Support for live backups using VSS—An important high-availability feature included with Windows Server Virtualization is the ability to back up running VMs using Microsoft Volume Shadow Copy Service. VSS takes a live snapshot of the VM's state without interrupting its operation.

7. Support for guest clustering—Windows Server Virtualization supports clustering guests either within the same node, which can be implemented using a shared SCSI adapter, or across different nodes, which requires a shared-storage solution that can be implemented using either an iSCSI or Fibre Channel SAN.

6. Support for host clustering—Host-clustering support is especially valuable for server consolidation environments. If the host goes down in such an environment, all the VMs running on that host will be unavailable. Host clustering lets you create a cluster resource containing the host's VMs. In the event of a failure, you can move the cluster resource to a backup node and restart all the VMs in about 10 seconds.

5. Support for snapshots—Windows Server Virtualization's support for snapshots helps bring the VM support in Windows 2008 up to the level offered by VMware's products. Snapshots let you make multiple point-in-time copies of the VM state and easily roll back to a previous state.

4. Support for 32GB memory per VM—With Virtual Server 2005 R2, VMs were limited to 3.6GB of memory. The virtual memory support for Windows Server Virtualization has been bumped to as much as 32GB per VM, allowing for much greater scalability. Remember, the host can't allocate more memory to a VM than it has available as physical RAM.

3. Support for 8-way virtual SMP—Another important scalability feature is the new support for virtual SMP. Unlike Virtual Server 2005, which supports only a single processor per VM, Windows Server Virtualization supports up to 8-way virtual SMP. The host must have at least as many physical CPUs (or cores) as you want Virtual-SMP machines to support.

2. x64 and virtualization-enabled hardware—In keeping with Microsoft's move toward 64-bit computing, Windows Server Virtualization requires an x64-compatible processor and the processor-based virtualization capabilities of either the Intel VT or AMD Virtualization processor. The product won't run on systems that don't support hardware virtualization.

1. Hypervisor-based architecture—Windows Server Virtualization brings with it an entirely new virtualization architecture. Like VMware ESX Server, Windows Server Virtualization uses a hypervisor-based kernel that runs directly on the system hardware. Unlike ESX Server, the Windows Server Virtualization hypervisor is ultra light-weight because it doesn't contain any device drivers or third-party code. Windows Server Virtualization also includes a new Virtual Service Provider/Virtual Service Client architecture that enables higher performance for VMs. Xen-enabled Linux can run as a guest OS and benefit from this new high-performance architecture.