Just think if you need RAID 0 (striping) or RAID 1 (mirroring) and set it. Have similar setup, you can see it here Optimal hard disk setup on Ubuntu 2 x SSD (Raid1) + 2 x HDDs (Raid1) few commands are also in a tread --> Optimal hard disk setup on Ubuntu 2 x SSD (Raid1) + 2 x HDDs (Raid1)