It sounds intuitive that you may just move the /var/lib/docker dir to another location and symlink it back but it won't work and you'll get an error.
How to move Docker Storage the Correct Way
This assumes that you want to use /mnt/raid as the new location.
1.) Stop Docker
systemctl stop docker
2.) Move /var/lib/docker
mv /var/lib/docker /mnt/raid/
3.) Edit the Docker daemon file
Specify the path you wan........