When you try to back up a virtual machine on a Windows Server 2008-based computer that has multiple virtual hard disks attached, the backup fails, and Hyper-V Writer error "0x800423f4" is generated

S’applique à : Windows Server 2008 DatacenterWindows Server 2008 EnterpriseWindows Server 2008 Standard


Backup of a Hyper-V virtual machine fails with error 0x800423f4 if the disk signature on a virtual hard disk is the same as a physical disk on the Hyper-V host.. Additionally, the following error message may be logged in the System log:
The number of volumes reverted does not match the number of volumes in the snapshot set for virtual machine '<VM name>' (Virtual machine ID <VM GUID>).


This problem occurs when one of the virtual hard disks that are attached to the virtual machine was created by using the option to copy the contents of a physical disk. In this scenario, the new virtual hard disk contains the same disk signature as the physical disk in the parent partition. During a backup process that involves Hyper-V VSS Writer, the virtual hard disks are mounted in the parent partition. This process fails for the affected virtual machines because of the disk signature collision. Therefore, you encounter the problem that is described in the "Symptoms" section.


To resolve this problem, manually bring the virtual hard disk online before you use the disk in a virtual machine. This step gives the disk a different disk signature.

Note The virtual machine must be turned off.

In Windows Server 2008 or in Windows Server 2008 R2, mount the virtual hard disk by using Disk Management. To do this, follow these steps:
  1. Click Start, click Run, type diskmgmt.msc, and then click OK.
  2. Click Action, and then click Attach VHD.
  3. Navigate to the affected virtual hard disk, and then click OK.

    Note The virtual hard disk will be marked as Offline.
  4. Right-click the disk, and then click Online.

  5. After the disk has been brought online, right-click the disk number, and then click Detach VHD.


For more information about the Msvm_MountedStorageImage class, visit the following Microsoft Web site: