During a GRT backup or restore of a Hyper-V virtual machine, the Virtual Hard Disk (VHD) is staged and mounted in order to inventory and extract the files for backup or restore.

Article:TECH148759  |  Created: 2011-01-21  |  Updated: 2013-04-18  |  Article URL http://www.symantec.com/docs/TECH148759
Article Type
Technical Solution


Environment

Issue



During a GRT backup or restore of a Hyper-V virtual machine, the Virtual Hard Disk (VHD) is staged and mounted in order to inventory and extract the files for backup or restore. 


Error



Backup Exec Error:

V-79-57344-38721 - 0xe0009741 - Failed to mount one or more virtual disk images. Restores that use Granular Recovery Technology may not be available from this backup set.

Windows Error:

 A virtual disk support provider for the specified file was not found.


Environment



To test for this condition, attempt to mount a VHD using Windows Disk Management. If Windows returns the second error listed above, apply the workaround listed below.


Cause



Per Microsoft, there is a timing issue with FSDepends.sys and with VHDMP.sys. This timing issue occurs when certain backup programs are installed on computers that are running Windows Server 2008 or 2008 R2. By default, the FSDepends.sys start value in the registry is set to manual.  When any third-party backup software loads its tape device driver, the software can sometimes result in FSDepends.sys and VHDMP.sys not initializing correctly.

 

To test for this condition perform the following steps.

 

 

1. Open disk management diskmgmt.msc

2. Click >Action >Create VHD

3. Click > Browse and type in a name for the vhd: C:\Temp\test.vhd

4. Set a small size of about 100 megs

5. Click OK

 If this works as expected you should now see a new virtual disk attached to your system.  Detach and delete the VHD, this article does not apply to you. 

 If you get an error : A Virtual Disk Provider for the specified file was not found, Then follow this fix below to ensure the ability to mount VHDs on this system.  

 


Solution



At the time of writing of this article, the issue was acknowledged and discussed in a Microsoft Knowledgebase Article available here:

http://support.microsoft.com/kb/2013544

To work around described in the above article is a registry modification (details follow).

Warning: Incorrect use of the Windows registry editor may prevent the operating system from functioning properly. Great care should be taken when making changes to a Windows registry. Registry modifications should only be carried-out by persons experienced in the use of the registry editor application. It is recommended that a complete backup of the registry and workstation be made prior to making any registry changes.
 

1)    Start Registry Editor (regedit)
2)    Locate the following registry key: “HKLM\SYSTEM\CurrentControlSet\Services\FsDepends”
3)    Under the “FsDepends” key, change REG_DWORD value “Start” from “3” to “0
4)    Restart the computer


Supplemental Materials

SourceError Code
Value0xe0009741
Description

Failed to mount one or more virtual disk images. Restores that use Granular Recovery Technology may not be available from this backup set.


SourceUMI
ValueV-79-57344-38721
Description

Failed to mount one or more virtual disk images




Article URL http://www.symantec.com/docs/TECH148759


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