Use logical volumes instead of loopback files

Set up the Logical Disks

$ sudo lvcreate --wipesignatures y -L 200G -n lv_docker_data vg
$ sudo lvcreate --wipesignatures y -L 10G -n lv_docker_metadata vg

Rewrite configuration

$ sudo cp -p /etc/sysconfig/docker-storage /etc/sysconfig/docker-storage.original
$ echo "DOCKER_STORAGE_OPTIONS = \
    --storage-opt dm.datadev=/dev/mapper/vg-lv_docker_data \
    --storage-opt dm.metadatadev=/dev/mapper/vg-lv_docker_metadata \
    --storage-opt dm.fs=xfs" | sudo tee /etc/sysconfig/docker-storage

Apply the change

$ sudo systemctl restart docker