After my post about my home office development environment using Hyper-V, I received comments and some emails regarding requirements, specifications and compatibility with virtual machines from Virtual Server 2005 R2 and Virtual PC 2007. Please note, that my main expertise is development (i.e. I am not a network or hardware guy), so my experience related to using Hyper-V only includes virtualization for development environments. I am going to summarize the high level details one should know about Hyper-V when considering an implementation. I would say that this is more for developers that wish to get up and running with Hyper-V, but this info is applicable to anyone using (or wishing to use) Hyper-V. I am going to write this post as a Q&A.

Q. What is Hyper-V?

A. Hyper-V is a server role within Windows Server 2008. It is a hypervisor-based technology that provides a scalable, reliable, and highly available virtualization platform. Hyper-V is only available on Windows Server 2008 x64 Editions as it requires a 64-bit processor that supports hardware-assisted virtualization and hardware data execution protection.
(parts paraphrased from http://www.microsoft.com/windowsserver2008/en/us/hyperv-faq.aspx)

Q. What is Windows hypervisor?

A. A core component of Hyper-V, Windows hypervisor is a thin layer of software between the hardware and the OS that allows multiple operating systems to run, unmodified, on a host computer at the same time. It provides simple partitioning functionality and is responsible for maintaining strong isolation between partitions. It has an inherently secure architecture with minimal attack surface, as it does not contain any third-party device drivers.
(copied from http://www.microsoft.com/windowsserver2008/en/us/hyperv-faq.aspx)

Q. What are the general system prerequisites for Hyper-V (software and hardware)?

A. Hyper-V requires Windows Server 2008 x64 (Datacenter, Enterprise or Standard) and an 64-bit processor that supports hardware-assisted virtualization and hardware data execution protection.

• Software Notes:
• Windows Server 2008 x64 (Datacenter, Enterprise or Standard). The version of Hyper-V included in the RTM version of Windows Server 2008 is not the RTM version of Hyper-V. You'll need to install Update for Windows Server 2008 x64 Edition (KB950050)
• Hyper-V cannot be enabled on systems running inside virtual machines or on x86 versions of Windows Server 2008.
• You can use Hyper-V MMC on Windows Server 2008 x86 editions and on Vista SP1 for remote management of Hyper-V systems.
• Hyper-V Updates (use as appropriate)
• Update for Windows Server 2008 x64 Edition (KB950050)
• Update for Windows Server 2008 (KB950050)
• Update for Windows Vista for x64-based Systems (KB952627) 
• Update for Windows Vista (KB952627) 
• Hyper-V Release notes (at the time of writing, this was published on July 3, 2008)
  
  
• Hardware Notes:
• Hyper-V requires an x64-based processor, hardware-assisted virtualization, and hardware data execution protection. Most newer 64-bit processors from Intel and AMD will do the job just fine as they support virtualization (AMD64 or Intel IA-32e/EM64T (x64) processors with hardware-assisted virtualization support), but be sure to look into a processors virtualization support before purchasing.
  (parts of this point copied from http://www.microsoft.com/windowsserver2008/en/us/hyperv-install.aspx)
• You can download SecurAble to see if your current processor supports hardware-assisted virtualization and hardware data execution.
• As for other hardware items, you can be the judge for your purposes. The more RAM you have the better. The faster your hard drive read/write speeds the better performance you'll get.

Q. How do I enable the Hyper-V within a Windows Server 2008 x64 edition?

A. See http://www.microsoft.com/windowsserver2008/en/us/hyperv-install.aspx.

Q. Which operating systems can run as a guest in Hyper-V?

A. See http://www.microsoft.com/windowsserver2008/en/us/hyperv-supported-guest-os.aspx for a listing.

Q. Can I run the Hyper-V role on a Server Core installation?

A. Yes, the Hyper-V can be enabled on a Server Core installation. I have yet to do this personally, but there are some brief notes about this at http://www.microsoft.com/windowsserver2008/en/us/hyperv-install.aspx.

Q. I have many existing virtual machines in Virtual PC 2007 or Virtual Server 2005 R2. Will they work in Hyper-V?

A. Yes. I have converted my virtual machines to work with Hyper-V, however I have not found it to be completely straight forward and there are things you need to know.

First, some gotchas that I found although I have not done exhaustive testing on this:

• The virtual machine additions for Virtual PC and Virtual Server 2005 R2 are not compatible with Hyper-V. You will need to uninstall them before using the VHD in Hyper-V.
• Depending on your version of Windows, you may need to re-activate your Windows OS. I really don't like this but the OS sees hardware changes and I believe this to be the cause. If anyone knows a way around this, I would be grateful.

General Steps to convert a Virtual PC 2007 or Virtual Server 2005 R2 VHD to work in Hyper-V:

1. First, make sure you have the fully up-to-date RTM version of Hyper-V.
2. Second, make sure your guest OS in Virtual PC or Virtual Server are fully patched with the latest service pack.
3. Copy the VHD file to a the location that you'll be running it with Hyper-V.
4. Open the copied VHD file in Virtual PC or Virtual Server.
5. Uninstall the Virtual Machine Additions. These are not compatible with Hyper-V and will cause problems.
6. You may be prompted to Activate windows again. Select ask again later as we will do this when it is running in Hyper-V.
7. Save the changes to the virtual machine and close Virtual PC or Virtual Server.
8. Fire up Hyper-V. Create a new virtual machine and attach the existing hard disk.
9. Install the Integration Components (these have been renamed as they used to be called Virtual Machine Additions)
10. Reboot the virtual machine in Hyper-V. When it comes back up, all should be well. I've noticed that networking doesn't work until a reboot when Integration Components are installed. 
11. Re-activate windows if necessary.

Q. I have my virtual machines running in Hyper-V, but my laptop, which I need to use sometimes for client presentations, has a 32-bit processor. What can I do?

A. To be honest, I have not tried converting a Hyper-V VHD for use in Virtual PC 2007 or Virtual Server 2005 R2 (will be doing so soon and will update this post with my findings) but I suspect if it is possible you'll have to uninstall the integration components first (similar to converting a VHD for use in Hyper-V from Virtual PC or Virtual Server - see above question). Another thing, that if this does work, it will only work with 32-bit operating systems as Virtual PC 2007 and Virtual Server 2005 R2 only support 32-bit guest operating systems. If anyone has done this, I would be grateful if you could please share your experiences as I need an answer myself. More on this soon when I do the research...

Q. Does the virtualization team at Microsoft have a blog?

A. Yes. http://blogs.technet.com/virtualization/

Q. Where can I get more information about Hyper-V?

A.

• Hyper-V on TechNet - http://technet2.microsoft.com/windowsserver2008/en/servermanager/virtualization.mspx.
• Hyper-V TechNet forum - http://forums.technet.microsoft.com/en-US/winserverhyperv/threads/. (Note: There is a sticky post indicating that "We are currently migrating this forum. Therefore we have disabled posting new threads and messages. Please be patient with us during this process. When migration is complete, this url will redirect to its new location."). So this can be used as a reference, but for the time being, not to ask questions.
• There are some webcasts available.
• Search the Internet. There are more and more blog articles written all the time about Hyper-V.