I mean to say, device mapper was the only solution which worked in a production setting for me. I no longer work with that company and so I can't tell how thos

I mean to say, device mapper was the only solution which worked in a production setting for me. I no longer work with that company and so I can't tell how those improvements would change the reliability. Presently I am using docker with btrfs on a low-throughput workload and it seems to work just fine. Tangentially related - I have been using OverlayFS without Docker for about a year now. It's pretty great. My read-layers can be on an NFS drive and the penalty for writes is relatively small. It basically gives me 90% of what I wanted from Docker in the first place.