Last time I tried was around 0.8, and aufs was not happy with xfs. I haven't tried having /var/lib/docker on ext4 and "/volumes" on xfs, I'll try if the need arises.

I run a few MongoDBs with volumes, but I'm not confident that I won't accidentally start two with the same volume, or that someone won't accidentally delete the volume, or .. or .. or.

As I've written to a sibling comment, I don't consider it a hard problem, but it hasn't been taken care of .. yet!