Errors accessing virtual cloud storage files

Notes about virtual cloud storage 

OneDrive, Google Drive, and similar cloud document editors/storage all operate alike in that user files are stored as on-demand files in the respective cloud server repositories. These locations which are not easily accessible by Magnus Box, regardless of whether a device can view and access them. Backing up these files is ONLY possible if you make a local copy of these files available to the Magnus Box client software. This may have unwanted consequences on network loading and local disk space.


To save on disk space, OneDrive (and some other cloud storage providers) use a system where some files are only "virtually" stored on the local disk, and are materialized from the cloud storage on-demand.

Error "Media is write protected" backing up OneDrive with VSS 

When you use the "Take filesystem snapshot" option in Magnus box, Magnus Box takes a VSS snapshot of the disk. This is a read-only snapshot.

When you back up the OneDrive directory with VSS enabled, OneDrive is not able to download files into the snapshot, because the snapshot is read-only. This causes the "Media is write protected" error message.

In this situation, your OneDrive data is not being protected by Magnus Box and is not available for restore.

You can work around this issue by creating two Protected Items: one with VSS enabled, that excludes the OneDrive directory; and a second one with VSS disabled, that only includes the OneDrive directory.

Note that if OneDrive needs to materialize a lot of data from the cloud, then backing up the OneDrive directory may cause a lot of data to be downloaded.

A future version of Magnus Box may avoid this issue by automatically disabling VSS for the OneDrive directory.

Error "Access to the cloud file is denied" backing up OneDrive 

If you encounter the "Access to the cloud file is denied" error message, this means that file in question does not exist on the local PC, and the OneDrive virtual filesystem driver is refusing to download this file on-demand for Magnus Box to read it.

At the time of writing, the only available workaround is to disable the "Files-On-Demand" feature in OneDrive. However, this may cause an unacceptable increase in local disk usage for some customers.

To disable the "Files-On-Demand" feature in OneDrive:

  1. Right-click OneDrive in the System Tray
  2. Click the menu icon -> Settings -> Settings tab -> "Files-On-Demand" section -> disable the "Save space and download files as you use them" option

Google Drive 

Error "G:\ not found" backing up Google File Stream items 

The Google File Stream app creates a virtual drive, e.g. G:\, that streams-in data from a business Google Drive account, over the internet, on-demand, without using any local disk storage, other than a small cache.

The virtual drive only exists for the interactive logged-in user session.

Magnus Box Backup runs all backups (both interactive and scheduled backups) using a service user account. Different login sessions have their own set of mapped drive letters, and the service session simply does not see that the virtual drive, G:\, exists.

It's still visible in the Magnus Box GUI file picker, which runs as the interactively logged-on user for performance reasons.

Ideally, it would be possible to mount the virtual G:\ drive "For all users", to resolve this issue.

Currently, this does not appear to be possible in File Stream:!topic/apps/iRH9lD9NM90

Note: If the virtual G:\ drive can be made available to all users, the process of backing up this data requires that it be downloaded first from the Google Drive, and this may cause large amounts of inbound network traffic.

There are third-party programs for mounting Google Drive as a drive letter that may support "All Users". StableBit Cloud Drive (commercial) may do this, as well as 'rclone mount'.

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