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

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.

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