Issue with docker directory after upgrade

Hi all,

I have following issue with /var/lib/docker:

Months ago I moved the docker folder from one partition (BTRFS) to another partition (ZFS) using the -g flag in DOCKER_OPTS. Everything was OK until a docker upgrade due to this setting was reset and docker used again the default folder to store containers and images. I have forgotten about this behavior and created new containers. Now I have some containers on the ZFS partition and some containers on the BTRFS partition pointing to the same volumes on my ZFS partition.

1.How can I move again the docker folder or at least the containers and images back to the ZFS partition avoiding any conflicts and without loosing data?
2.How can I prevent docker to use the default settings every time there is an upgrade?