Is there a way to leverage btrfs's advanced features (COW, snapshots, etc.) to continuously backup/mirror my main storage volume to an external USB HDD?
ideal btrfs storage scheme to incorporate external USB HDD as backup media
backup;btrfs
The btrfs Wiki lists several Incremental Backup tools that are suitable in response to this question.btrbk is the one I am currently using and it meets most of the requirements mentioned in the question.I say most because the question was not clear regarding the differences between snapshots and a true versioning file system (which btrfs is not). But the question is specific to btrfs and the best btrfs solution is frequent snapshots together with a tool that automates the creating the snapshots, send-receive transfers and pruning the snapshot timeline.