Error "Unable to mount one or more virtual disk images" appears for a Hyper-V backup job

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  • Article ID:000017663


Microsoft's Windows Server 2012 includes a new VHDX file format, which supports virtual disks that are up to 64 TB in size. A Backup Exec server cannot be installed on a computer that runs Windows Server 2012. Backup Exec cannot mount VHDX files that are larger than 2 TB. When VHDX files are larger than 2 TB, then Backup Exec does not support application-level Granular Recovery Technology (GRT) or file/folder-level GRT.


Error Message

V-79-57344-38759 Unable to mount one or more virtual disk images. Support for VHDX files is not present in this version of the Windows Operating System. Backups that were enabled for Granular Recovery Technology may not be available for restore.



Backup Exec can mount VHDX files that are smaller than 2 TB by processing them as VHD files. Therefore, application-level and file/folder-level GRT are available for VHDX files that are smaller than 2 TB. Additionally, the entire virtual machine can be restored regardless of the size of the VHDX file.


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