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Hyper-V FAQs

Eliminate virtualization confusion about scalability, migration, and other topics

Executive Summary:

Comparisons of Microsoft Hyper-V to Virtual Server 2005 and VMware’s ESX Server stir up confusion. These Q&As help you evaluate Hyper-V's requirements, such as how you upgrade or migrate from other VMs, and show you some differences are between Hyper-V, Virtual Server 2005, and ESX Server.

Hyper-V is Microsoft’s newest entry into the enterprise virtualization arena. It’s the successor to Microsoft Virtual Server 2005 R2. Comparisons of Hyper-V to Virtual Server and VMware’s ESX Server always stir up a lot of confusion. To help eliminate some of that confusion, here are 10 of the most frequently asked questions about Hyper-V.

10. Does Hyper-V run on top of Windows Server just like Virtual Server 2005 does?—No. Virtual Server 2005 is a hosted virtualization product, so the virtualization support is provided in a software layer run by the host OS. Hyper-V uses a hypervisor-based architecture that runs directly on the system hardware: There’s no intervening host OS.

9. Can I upgrade to Server 2008 and get Hyper-V?—In most cases, you won’t be able to upgrade older servers to take advantage of Hyper-V. Hyper-V requires an x64 processor with hardware-assisted virtualization capabilities (i.e., Intel’s Intel-VT or AMD’s AMD-V). Systems more than a year or two old aren’t likely to have such processors.

8. Does Hyper-V support non-Windows OSs as guests?—Yes. In addition to Windows OSs, Hyper-V will support all Xen-enabled Linux distributions as first class virtual machines (VMs). You can find a list of the supported Hyper-V guest OSs at

7. Does Microsoft’s licensing for running a virtual environment under Server 2008 Enterprise Edition and Datacenter Edition apply only to Hyper-V?—No. This licensing applies no matter what virtualization product is used, including VMware’s ESX Server. Microsoft allows up to four active VMs under Server 2008 Enterprise Edition and an unlimited number of active VMs with Server 2008 Datacenter Edition.

6. Is Hyper-V more scalable than Virtual Server 2005 R2?—Yes. Hyper-V runs on 64-bit hardware and it supports virtualization hosts with up to 2TB of RAM and VMs with up to 64GB of RAM. This is far above Virtual Server 2005 R2’s limit of 3.6GB of RAM per VM. In addition, Hyper-V supports VMs with up to four virtual CPUs; Virtual Server 2005 R2 is limited to single-processor VMs.

5. Are Hyper-V and ESX Server essentially the same?—No. Both products are hypervisor-based, but the implementation is quite different. ESX Server device drivers are part of the hypervisor itself. Hyper-V uses a microkernel implementation with no device drivers in the hypervisor: They’re in the parent partition.

4. How do I migrate Virtual Server 2005 VMs to Hyper-V?— Uninstall Virtual Machine Additions from the VM you want to migrate. Next, move the Virtual Hard Disk (VHD) image to a location accessible by the Hyper-V Manager and build a VM that’s comparably configured. Finally, when prompted to create a new virtual drive, select the existing Virtual Server 2005 R2 VHD file. However, you’ll be prompted to reactivate because Windows will detect a massive hardware change.

3. Does Hyper-V have tools to convert VMware VMs to Hyper-V VMs?—No. Microsoft’s Virtual Server Migration Toolkit requires Automated Deployment Services, making it too difficult to use. Microsoft’s System Center for Virtual Machine Manager converts VMware VMs to VHD image format, but it isn’t free. You can find free and commercial third-party tools as well.

2. Is Virtual Machine Additions required with Hyper-V?—In Virtual Server 2005, Virtual Machine Additions moved part of the VM processor into the host kernel. Hyper-V’s use of hardware-assisted virtualization makes that unnecessary. After the guest VM has been installed, you can optionally install integration components that add functions such as a data exchange service. For Windows Server 2003, integration components are necessary to get device drivers for Hyper-V’s synthetic devices.

1. How do I get the final release version of Hyper-V?—The version of Hyper-V that shipped with Server 2008 was prerelease code. The final release of Hyper-V will be distributed from Microsoft via Windows Server Update Services. VMs created under the Hyper-V beta will need to be rebuilt, but VMs created using the release candidate should be compatible.

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