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Matt McSpirit on Virtualisation, Management and Core Infrastructure


15 things you always wanted to know about Virtual Server (But were afraid to ask)...

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A big thanks goes to Jeff Woolsey, one of the Lead Program Manager's here at Microsoft, for compiling this excellent list of the top 15 questions asked around Virtual Server.  Without further ado, lets start with number 15...

15 - Is it true that Virtual Server 2005 R2 EE is now FREE?

Yes, that is indeed correct. Virtual Server 2005 R2 EE has been free since April 2006.  We have had more than 340,000 downloads to date.  If you are interested in discovering the benefits of virtualisation, through Virtual Server, head on over to

14 - I’ve just installed Virtual Server. Where are my virtual machines and operating systems?

Virtual Server is an enabling technology and product.  Virtual Server provides the virtualisation layer giving you the ability to run multiple virtual machines on top of a Windows Server host.  Once you’ve installed Virtual Server, you must create virtual machines and install operating systems just as if someone gave you a computer with a completely blank hard drive.  Virtual Server does not include guest operating systems.

13 - How do you back up virtual machines?

There are two ways to backup a virtual machine. Each method has pros and cons and users can determine which method best suits their business requirements.

Method 1
Backup each virtual machine from within each guest operating system.  Install the backup software in the guest operating system and backup each virtual machine in the same way you would a physical computer.

The advantages to this method are:

  • This backup can be performed “live” on running virtual machines
  • If an IT organization has a standard backup process, this simply uses the existing process.  There aren’t two different methods to backup physical versus virtual machines.  IT departments like this consistency.

The disadvantages to this method are:

  • Backup software licenses need to be purchased for each virtual machine
  • Backing up the each virtual machine may take longer than backing up all virtual machines from the host operating system

Method 2
Backup all virtual machines from the host operating system.  The second method is to backup the Virtual Server host. You can backup the entire host computer and all virtual machines at once, but this can only be performed on stopped/saved virtual machines.  The downside is that this is not a “live” backup. You MUST shutdown or save state the virtual machine to perform the backup.  To backup the host operating system without stopping/saving a virtual machine would be like pulling the power code on a physical computer and then making a copy of the HD. The HD might boot next time but checkdisk would certainly need to run and it is likely there is corrupt user data. 

Here’s why:

The issue is that when a backup is performed on the host, this operation backs up files on disk but does not include the memory in use by the running virtual machine.  For example, if you allocated 2GB to a virtual machine and backed up the host operating system, there is potentially 2GB of virtual machine data not backed up! To safely backup a virtual machine, the entire state of the virtual machine must be backed up which includes:

  • the contents of the virtual machine’s memory
  • the virtual hard disk(s)
  • the virtual machine configuration

It is possible that someone could automate this process. For example, a script could be written to save the state of the virtual machines and backup the host operating system, but such a script is not included with the product.

The advantage to this method is that:

  • The backup method may be faster

The disadvantages to this method are:

  • If not performed properly, this can result in the loss of data.
  • The backup is not live. All of the virtual machines need to be saved at some point.
  • This backup process is virtual machine specific resulting in two backup processes.  One method for physical machines and one for virtual.

IMPORTANT NOTE: Method 2 is not recommended if you’re running a domain controller in a virtual machine. If you are using a domain controller in a virtual machine, always use Method 1. For more information on using a domain controller within Virtual Server, see the following whitepaper:

12 - How many virtual machines can you run per physical processor?

There is no one size fits all answer to this question. There are simply too many variables.  Performance of virtual machines depends on a multitude of factors including, but not limited to:

  • The amount of RAM in the physical server
  • The amount of RAM assigned to each guest
  • The workload running in the guest operating system
  • The workload running in the host operating system
  • The number of running virtual machines
  • The total workload of all running virtual machines
  • The guest operating system
  • The number of host NICs installed and used by virtual machines
  • Speed of host NICs (100Mb vs. 1Gb, switched vs. non-switched)
  • Speed of the host processor
  • Number of host processors
  • Number of disk spindles
  • Type of storage (IDE, SCSI, Fibre, iSCSI, RAID 5, etc)
  • Number of Host Bus Adapters
  • Configuration of Virtual Server CPU Resource Allocation Settings

As a broad generality, we’ve heard of people using anywhere between 1 to 10 virtual machines per physical processor with the average being 4 to 6. (In the case of 10 virtual machines, these were very lightly loaded NT servers.)  However, as stated above the number of virtual machines really depends on the multitude of factors above.

11 - Can you run a domain controller within a Virtual Server virtual machine?

Yes.  For detailed information on using a domain controller within Virtual Server, see the following whitepaper:

10 - Do we have performance tips for Virtual Server?

Of course! - Visit KB:;en-us;903748

9 - What Microsoft products are supported within Virtual Server?

KB: 897613 Microsoft Virtual Server Support Policy:

KB: 897614 Windows Server System software not supported within a Microsoft Virtual Server environment:

8 - Are additional versions of Virtual Server planned?

Yes. We are working on the next release of Virtual Server.  It is called, Virtual Server 2005 R2 SP1 and is publicly available in beta form today at

Some of the key points of this release include:

  • Support for hardware assisted virtualization in the form of AMD-V and Intel VT
  • Support for Volume Shadow Service (VSS)
  • Ability to mount virtual hard disks (vhds) in the host OS
  • Integration with Active Directory
  • and more…

7 - I’ve heard that Virtual Server 2005 R2 now supports clustering, where can I find more information?

You can find the information by following this link.  The document describes a simple configuration in which you use Microsoft Virtual Server 2005 R2 to configure one guest operating system, and configure a server cluster that has two servers (nodes), either of which can support the guest if the other server is down.

6 - Does Virtual Server support Symmetric Multi-Processing (SMP) in the guest?

No, unfortunately not. Microsoft have publicly stated that this will be providing this feature in our next generation, Windows Virtualisation.

5 - Does Virtual Server support USB?

No, unfortunately not.  Again, we have stated publicly that we are working on this feature for our next generation, Windows Virtualisation.

4 - Does Virtual Server support 64-bit hosts and guests?

Virtual Server 2005 R2 adds support for x64 64-bit hosts.  Unfortunately, Virtual Server does not support 64-bit guests.  We have already stated publicly that we will provide this feature in our next generation, Windows Virtualisation.

3 - What is Windows Virtualisation? When does it arrive?

Windows Virtualisation is virtualisation technology incorporated into Longhorn Server.  The current plan of record for Windows Virtualisation is that it ships within 180 days of the Longhorn Server release.

2 - What will I need to run Windows Server Virtualisation?  What are the system requirements?

Windows Server Virtualisation has the following system requirements:

  • Longhorn Server x64 Edition AND
  • System with hardware assisted virtualisation (either Intel VT or AMDV (formerly Pacifica))

To be explicit, Windows Server Virtualisation will NOT run on:

  • Windows Vista
  • Longhorn Server 32-bit (x86) or Itanium (IA-64) versions
  • Systems that don’t have Intel VT or AMD-V (Pacifica)

1 - What are some of the key differences between Virtual Server R2 and Windows Server Virtualisation?


Virtual Server 2005 R2

Windows Server

32-bit VMs?



64-bit VMs?



Multi-core VMs?


Yes, up to 8 core VMs

VM memory support?

3.6 GB per VM

More than 32 GB per VM

Hot add memory/processors?



Hot add storage/networking?



Can be managed by SCVMM?



Cluster support?




Yes, COM

Yes, WMI

Number of running VMs?


More than 64.
As many as hardware will allow.

User interface

Web Interface

MMC 3.0 Interface

Thanks again to Jeff Woolsey for this information.

  • Would be nice to see the improvements intel VT or AMDV brings in virtualization for instance in terms of supported VM's Would be nice to get more infos over SCVMM, and Windows Server Virtualisation Would be nice to have more infos about the future integration (backup VHDI, VSS integration, ... ) Would be nice to have more infos to see how MOM would select thanks to MP candidate at virtualization

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