This issue occurs during an Agent for Microsoft Hyper-V backup on a virtual machine where the VHD contains a Dynamic disk on the Guest.
When GRT (Granular Restore Technology) is enabled, the job completes with the following exceptions:
V-79-57344-38721 - Failed to mount one or more virtual disk images
V-79-40960-38513 - Failed to mount one or more virtual disk images
Debug the Backup Exec Remote Agent Service on the Hyper-V host to verify if the following errors appear in the debug log:
(BEREMOTEXX.LOG) debug log on Hyper-V Host:
[mounter] - Just mounted (C:\TEMP\Backup Exec\01cb88fdf4febdf0\Virtual Files\C\ClusterStorage\Volume2\ESCDC.VHD) on (\\?\PHYSICALDRIVE6)
[mounter] - MSVSVirtualSystem::MountDisks: file "C:\TEMP\Backup Exec\01cb88fdf4febdf0\Virtual Files\C\ClusterStorage\Volume2\GUEST_F.VHD" Signature: 0X54F3E004 Partition Count: 1 Dynamic: True
[mounter] - Total Virtual Disks Mounted: 1
[mounter] - VDiskMounter::MountAllDisks:failed VirtualSystem::Initialize()
[mounter] - Error mounting disks (0xe0009741)
[fsys\ntfs\img_pdi] | Error mounting disk(s): E_IMG_FS_FAILED_TO_MOUNT_VIRTUAL_DISK (0xe0009741).
[fsys\ntfs\img_pdi] | Creating DDB for Virtual Machine of failed mount
| Exit point of IMG_PDI_FSYS::ImgPdiFsys::CreateDDBForVMMachine hit: (0x00000000)
[fsys\ntfs\img_pdi] | Returning no more files because of previous mount error
[fsys\ntfs\img_pdi] | returning SUCCESS for previous mount error
[fsys\ntfs\img_pdi] | Returning delayed mount error during open call: E_IMG_FS_FAILED_TO_MOUNT_VIRTUAL_DISK (0xe0009741)
In the above debug log the statement "Partition Count: 1 Dynamic: True" indicates the VHD contains one partition and the disk inside the guest is a dynamic disk (Figure 1)
The Agent for Hyper-V Server does not support GRT backups of Virtual Machines that contain Dynamic disks inside the guest. Perform a non-grt backup of the Virtual Machine or change\convert the disk to a simple or basic volume. Please refer to the Backup Exec 2010 R2 Software Compatibility List (SCL) (TECH137682) or the Backup Exec 2012 SCL (TECH175581)
Backup to Tape with GRT enabled.
Backup to Deduplication Folder with GRT enabled.