for CentOS 6 a simpler solution is
edit
/etc/syscofig/docker
add "-g /your/storage/dir" to other_args=
will looks like:
other_args="-g /your/storage/dir"
execute:
cp -r /var/lib/docker /your/storage/dir
to copy everything (image/container) to new location
execute:
service docker restart
vola!