Error "not a supported backup storage location" backing up System State to a USB flash drive

The "Windows Server System State" and "Windows System Backup" Protected Item types in Magnus Box inherit some restrictions from the underlying technology (wbadmin).

It's not officially possible to spool the backup job to a USB flash drive:

"You cannot store backups on USB flash drives or pen drives." - https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2008-R2-and-2008/cc753528(v=ws.11)

This is a preventative measure in case the drive is removed mid-backup.

The following workarounds are available:

  1. Modify the flash drive to appear as a non-removable disk

For more information, please see https://social.technet.microsoft.com/Forums/windowsserver/en-US/c39c050f-d579-4222-8ad1-44d2ff53882b/windows-backup-cannot-see-usb-flash-drive?forum=windowsbackup#03e336a4-bc68-46f6-9a4c-be6907903da6

    2. Create a shared network directory on the flash drive, and tell Magnus Box to use the UNC network path as the spool directory instead

For more information, please see https://social.technet.microsoft.com/Forums/lync/en-US/e1f0fa4e-5fb0-4749-82d6-16b1bd427495/when-will-windows-server-backup-allow-usb-flash-drives-as-a-target?forum=windowsbackup#fc8affd9-378a-447e-a36e-c5af0bb1e40b