assuming device is in /dev/sda1
sudo apt install mdadm
sudo mdadm --create --verbose /dev/md0 --level=mirror --raid-devices=1 /dev/sda1
sudo mkdir -p /mnt/raid1
sudo mkfs.ext4 /dev/md0
sudo mount /dev/md0 /mnt/raid1/
ls -l /mnt/raid1/
sudo nano /etc/fstab
#add this -> /dev/md0 /mnt/raid1/ ext4 defaults,noatime 0 1
sudo mdadm --detail --scan | sudo tee -a /etc/mdadm/mdadm.conf