At CoreOS and we tried really hard to make btrfs happen, but it really came down to how different it operated than other file systems. It was mainly a UX issue

At CoreOS and we tried really hard to make btrfs happen, but it really came down to how different it operated than other file systems. It was mainly a UX issue and thus fell into my lap. The major issue is that regular debugging tools that folks have been using forever like `df -h` aren't just non-functional, they actively misrepresent the state of the file system. The most common example is indicating that you have plenty of free space when in fact you're out. We had to write a lot of documentation to teach people how btrfs works and how to debug it: https://coreos.com/os/docs/latest/btrfs-troubleshooting.html https://coreos.com/os/docs/latest/btrfs-troubleshooting.html The second major issue is that rebalancing requires free space, which is the problem that most folks are trying to fix with a rebalance operation. Catch-22 in the worst way. Containers vary in size and can restart frequently, churning through the btrfs chunks without filling them up, leaving around a lot of empty space that needs to be rebalanced.