mdadm

1. start raid

mdadm --assemble --scan

2. start raid in case if you do not have /etc/mdadm.conf (should have raid UUID)

mdadm /dev/md0 --assemble -u e6d85d3d:d20ddcfc:c7cxxxxx:6a0xxxx

3. generate /etc/mdadm.conf

 mdadm --detail --scan >> /etc/mdadm.conf