Instructions

Create Longhorn volume
Mount longhorn volume to a node (recommend worker node)
Log into selected worker node
Create temporary folder for migration sudo mkdir /tmp/folder
List the disks to format sudo fdisk -l
Format the disk sudo mkfs -t ext4 /dev/sdx
Mount the new disk to tmp folder sudo mount /dev/sdx /tmp/folder
Copy data from Docker Host to new drive (substitute your values below) sudo rsync -avxHAX username@DockerHostIP:/home/ubuntu/docker/some-directory/* /tmp/folder