Well I have to say, that we have been running discourse in the btrfs filesystem for almost a month without any single problem.
It works smoothly.
The btrfs drivers of docker seem to work perfectly.
It would be great if some other people tests discourse running over btrfs and btrfs support could be integrated under discourse distribution.
We stop the forum for a moment, take the snapshot using btrfs (a couple of senconds) and run it again.
Then we make an external backup of the taken snapshot.
It seems to work perfectly.
I have restored the backup in another machine to test and it works.
The