Unable to mount disk: unsupported disk type

It is critical that the "Before You Begin" page regarding Guest File (Windows) Restores is reviewed to confirm restore compatibility.

There are specific requirements listed in the user guide regarding restores from volumes using ReFS or Data Deduplication.

The following steps should only be performed after confirming that the volumes of the backed-up server are compatible with the Mount Server.

Reboot the Mount Server

There are several processes involved in the Guest Files (Windows) Restore operation. Failures may indicate a software or OS level issue. It is therefore advised that as the first step of troubleshooting, the Mount Server should be restarted.

Reinitialize VDK driver on Mount Server

The VDK driver is used by Veeam Backup & Replication to help the Windows OS mount VMDK files and view their content. This driver is exclusively used with vSphere VMs; this step is not necessary for Hyper-V environments.

Perform the following steps on the Mount Server specified in the repository settings where the backup files are stored.

1. Open an Administrative Command Prompt (or PowerShell)
2. Navigate to: C:\Program Files\Common Files\Veeam\Backup and Replication\Mount Service
3. Execute the following command to uninstall the VDK driver:
   
   vdk remove
   
   
4. Execute this command to install the VDK driver:
   
   vdk install
   
   
5. Reboot (optional)

Review Anti-Virus Exclusions on Mount Server

Antivirus may interfere with the Guest Files (Windows) Restore operation. This can have effects ranging from performance degradation to complete failures due to antivirus locking files or preventing access.

Ensure that the following antivirus exclusions are in place on the Mount Server associated with the repository where the backup files are stored.

How to configure antivirus exclusions to prevent interaction with Veeam Backup & Replication

Manually Clear FLR Cached Files on Mount Server

During a Guest Files (Windows) Restore files are cached in temp folders. If the file-level restore process is not terminated cleanly, those temporary files can be left behind and cause issues.

Perform the following steps on the Mount Server specified in the repository settings where the backup files are stored.

1. Navigate to C:\Windows\Temp
2. FLR temp files will be stored in folders with 9 characters a dot and 3 more characters (e.g. ni0awns0.xgw, 0pob3q21.dc0, pynkisu0.3vl). Contained in this folder may be a file starting with "veeamflr" and having the extension ".flat" (e.g., veeamflr-f1d5438a3b610f99-0000.flat)
3. After confirming no restore operations are occurring, remove the folders mentioned in step #2.

Workaround

If the Windows FLR (Guest Files (Windows) Restore) continues to fail after attempting the steps outlined in this KB, please attempt a Guest Files Restore > Linux and other...

Other Guest Files (Windows) Restore messages:

This warning indicates that the Mount Server, specified in the repository settings where the backup files are stored, is running an OS that does not support the ReFS version in use by the server that was backed up. To ensure ReFS compatibility, edit the repository and change to a Mount Server running the same or newer OS than the backed-up server.

This warning indicates that the Mount Server, specified in the repository settings where the backup files are stored, is running an OS that does not have the Deduplication role enabled. Enable the deduplication role on the Mount Server so that it can read the Deduplicated volume.

Review: ‘The revision level is unknown’ upon Guest OS File restore