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

Veeam Backup & Replication
8.x, 9.x
Last Modified:


A Backup contains a VM with Windows 2016 as the GuestOS and Deduplication is enabled for some (or all) of the drives. The Backup completes without Warnings or Errors, but when performing a Windows File Level Restore, you receive the following message:
“Failed to transfer C:\VeeamFLR\VMName_index\Volume#\filename. The revision level is unknown”. Clicking ‘Continue’ skips the file.
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If you navigate to C:\VeeamFLR and the locate the same volume, the file will be seen, but it won’t be restorable, producing the error: Error 0x80070519: The revision level is unknown.
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To resolve this issue, please do the following:

  1. Install remote Veeam console on Windows 2016 with deduplication feature enabled: https://helpcenter.veeam.com/docs/backup/vsphere/install_console.html?ver=95
  2. Change mount server for these backups to the Windows server 2016 with deduplication enabled: https://helpcenter.veeam.com/docs/backup/vsphere/repository_mount_server.html?ver=95
After making these changes, restores should be successful.

More Information

As part of the File Level Restore workflow, disks of the VM are first mounted from the backup file to the machine on which the Veeam Console was used to start the restore process. When the files are chosen, Veeam creates an additional mount point on the Mount Server associated with the Backup Repository where the backup files are located.

Both machines (the one with the Console and Mount Server) need to understand deduplication volumes format in order to perform the restore successfully. Unfortunately, the Windows 2012R2 deduplication engine is different than that in Windows 2016, which is why we can see the contents of the disk (as opposed to server with no deduplication enabled), but the error occurs upon restoring.

Please be aware that we’re making changes which will restrict access to product updates for users without an active contract.


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