Backup failed: One or more disks for this virtual machine are unsupported.


This article provides instructions for resolving VMware backup failures caused by unsupported disks.


Using a third party tool to convert a VHD (Hyper-V) to a VMDK (VMware) can result in a VMDK with a provisioning type that is not supported by VMware.  Attempts to back up these disks on a Unitrends appliance fail with the following error: Backup failed:  One or more disks for this virtual machine are unsupported.   



To resolve this error:

  • Ensure that the VMDKs use one of the following provisioning types supported by VMware:
    • Thick Provision Lazy Zeroed
    • Thick Provision Eager Zeroed
    • Thin Provision

The recommended option for resolving this error is to change the provisioning type for the converted disk.  For instructions, see the VMware article Changing the thick or thin provisioning of a virtual disk.  If the original VHD is still available, you can also resolve the issue by redoing the conversion.  See the attached article for details.


For more detailed information on backup failures and performance issues see Unitrends KB 5062 - Backup Failures and Performance Issues


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