What is an effective way to ensure a OneDrive backup of all files? 

To ensure a comprehensive backup of all OneDrive files, we recommend using Vaultastic for a simple yet effective strategy -start by performing a complete backup of all files from your users’ OneDrive accounts. Following this, set up daily incremental backups to capture any changes or new files added that day. This approach guarantees that your critical information is continuously protected, providing full redundancy and safeguarding against data loss.

Note that the incremental backup ignores files deleted on OneDrive, thus ensuring that the archive has complete content.