Windows Server 2012 - Backup files on a USB drive without a drive letter

Question

So, I have been backing up my server to a 7TB USB drive. Backup is configured as Bare Metal recovery with advanced option VSS Copy Backup. Everything is working fine and the USB drive is gradually filling up with each daily backup. My question is, soon I will have to delete some of the very old backups to gain more space to store my daily backups. I can see the space utilized by the backups, however, I am unable to access this drive or display the files. Does anyone know the best technique to remove files from a drive with no assigned drive letter?

Answer 1

The following answer is based on your comments to your original question. If your backup software removes the drive letter, I am afraid that we cannot prevent it from doing so, and the only options are a few workarounds.

Please note that I don't know Windows Server 2012, but the following techniques should work under that version, too.

Other file manager software

Instead of Windows Explorer, you could use another file manager software which gives you access to a drive's contents without a drive letter. Personally, I am not aware of such software, but it is probably out there.

This would be the only method to do what you have asked for, i.e. access files on a drive without drive letter or other mount points.

Mountvol

The following text outlines methods to assign and remove a drive letter or directory mount point very conveniently by either just a double click or completely automatically after the backup. While this does not directly answer your question, I believe that it is an acceptable solution to your problem.

Since ages, Windows desktop and server versions include a tool called mountvol, which can be used to manage drive letters from the command line. You could use it the following way:

Preparation (only once)

Attach the USB drive and manually assign a drive letter. Open a command prompt with administrative rights and type mountvol without any options. Since this is an error, mountvol outputs usage instructions and a list of available volume names along with their current mount points.

Identify the entry where the mount point is the drive letter you have assigned, and note the volume name. This is the volume name of your USB drive, which remains constant, i.e. will be the same each time you attach it.

Now create a batch file which just contains one line like

mountvol X: \\?\Volume{221a9d0e-ad88-4143-88ca-b54d3d4fce7d}\

where the last part is the volume name you have noted in the previous step. Save that batch file on your desktop and name it mount-usb.

Create a second batch file which just contains one line like

mountvol X: /D

and save it on your desktop under the name unmount-usb.

Usage

Just double click mount-usb. This will mount your USB drive under the respective drive letter. When you are finished using it, double click unmount-usb. This will remove the respective drive letter.

Improvements and remarks

• I did not explicitly test what happens when you try to assign a drive letter which already is assigned elsewhere, but I am pretty sure that mountvol in this case just outputs an error message and returns a non-zero exit code. You can catch both of them in a more sophisticated batch file to handle errors in a clean way.

• You don't need to give only a drive letter as mount point. That is, mountvol can handle directory mount points as well. For example, you could create a directory d:\usb and use d:\usb instead of X: in the above example.

• The final step would be to initiate the backup from within a batch file, and in that batch file, put the command line given above after the line which starts the backup. That way, the USB drive would be mounted with drive letter / mount point automatically each time after the backup has run.

  For this to work, you probably have to remove the scheduling from the backup job itself, and instead use Windows' task scheduler to schedule the execution of the batch file.

  I have only mentioned this for the sake of completeness. Personally, I would stick without that, because it is probably a good idea to have the USB drive without a drive letter as long as you don't need it. Furthermore, I can't help you with the command line for the backup job, because I don't know that backup software, and I don't have Server 2012, so I can't try it.

• As a final remark, the backup software removing the drive letter is more a protection against user mistakes than a protection against malware:

  If you can use mountvol to assign a drive letter, malware can do the same (via mountvol or via Windows API). The only obstacle would be the UAC prompt, but if you have managed to start the malware with administrative rights, even that wouldn't help.

  Alternatively, malware could attack an insecure local process which already has administrative rights and let it execute commands like mountvol.

  There is only one reliable method against malware having access to the backup: After the backup, remove the backup drive from the PC and store it in a safe place.

  This would also prevent damage in some situations people mostly become aware of when it is too late:

  Your backup won't help you when your backup drive is placed besides your PC, and both get stolen together, or there is a house fire or a flooding, or a lightning destroys your backup drive along with your PC, which is not uncommon and could happen via the USB data connection as well as via the power outlet. So really use two backup drives, exchange them at least once per week (adjust according to your risk-to-effort ratio), and keep one of them outside your home.