Backup Windows volume mounted to mount point

[Lad]

Hello,

Bareos server is installed on CentOs 7.x.

Agent is installed on Windows 2012.

Windows disk D: contains data and also mount point (D:\mountpoint ) to which the volume (without drive letter) is mounted.

Backup job of disk D: ends with error:

JobId 105: Fatal error: No drive letters found for generating VSS snapshots.

JobId 105: Error: VSS API failure calling "BackupComplete". ERR=Object is not initialized; called during restore or not called in correct sequence.

JobId 105: Fatal error: Director's comm line to SD dropped

Fileset definition:

FileSet {

  Name = "server_data"

  Include {

    Options {

      Signature = MD5 # calculate md5 checksum per file

      #Compression = LZ4

      noatime = yes

      onefs = no

      IgnoreCase = yes

    }

    File = "D:/"

  }

}

Any idea how to solve it? Should I assign drive letter to the volume?

Thanks

Regards

Lad