Hyper-V Release Notes

Applies To: Windows Server 2008

These release notes address known issues about Hyper-V. For other information, see Hyper-V.

Known Issues

The following are the known issues for the release of Hyper-V distributed as ”Hyper-V Update for Windows Server 2008 x64 Edition” (KB950050) (https://go.microsoft.com/fwlink/?LinkId=139066). For known issues related to subsequent releases of Hyper-V, see the release notes for Windows Server.


  • The data on the physical disk attached to a virtual machine, or on the Internet SCSI (iSCSI) disk attached to the guest operating system will not be included in backup when a virtual machine has either a physical disk or an iSCSI disk attached. To fix this issue, utilize backup agents inside the virtual machine and individually back up each virtual machine as if it is a physical computer.

  • Virtual machines that have dynamic volumes inside the guest operating system are supported for offline backup only when the guest operating system is configured to use dynamic disks in Disk Manager. When attempting a backup of such a virtual machine, it is saved and subsequently resumed, during the backup process. Even if the virtual machine is running, only an offline backup is taken. To avoid this issue, when using online backup, one should only use a basic disk. To fix this, either use offline backups or convert the dynamic disk to a basic disk.

  • If you restore a Volume Shadow Copy Service (VSS) based backup of a virtual machine while it is running, the virtual machine may end up in an inconsistent state. To avoid this issue, ensure that the running virtual machine is not selected in the backup application before starting the VSS restore operation, ensure that the virtual machine is turned off prior to starting the VSS restore operation or, if doing a system-wide restore, ensure that all of the virtual machines are turned off.


  • If the Hyper-V authorization store is located in Active Directory, then the removal of a user from a role does not take immediate effect. Either the server running Hyper-V (the computer that runs the Virtual Machine Management Service (VMMS)) or Active Directory needs to be rebooted to apply the changes. To avoid this issue, use an XML file as the store type. To fix this issue, reboot the Hyper-V server hosting VMMS, restart VMMS and Network Virtual Service Provider Windows Management Instrumentation (NVSPWMI) services or reboot Active Directory.


  • If you try to restart or reset a virtual machine when the physical computer is low on available memory, the virtual machine may be turned off instead of restarted. To avoid this issue, retain at least 512 MB of memory for use only on the physical computer. To fix this issue, you can try to start the virtual machine. If this does not work, you can modify the virtual machine settings to reduce the amount of memory assigned to the virtual machine.

  • While connecting through Virtual Machine Connection under a Remote Desktop session, the use of CTRL+ALT+DEL will not work. To avoid this, use CTRL+ALT+END, avoid using Virtual Machine Connection under Remote Desktop or use the CTRL+ALT+DEL options found on both the toolbar and Action menu.

  • You may encounter issues when attempting to attach virtual hard disks (VHDs) and ISOs to a virtual machine from a network share. To avoid this issue, ensure that both the Hyper-V server and the network server are members of the same domain. The network share requires read access for ISOs and read/write access for VHDs for both the user and computer account of the server running Hyper-V. If you are attempting this from a third computer (not utilizing the user interface on the server running Hyper-V), constrained delegation for Server Message Block (SMB) between the server running Hyper-V and the network file server must be enabled.