RAID one delivers full redundancy. With 2 drives, it will mirror all details to the opposite generate, with 3 drives, it will eventually mirror to both equally another drives. Ex. You've two 1TB drives in a RAID one, you'll have 1TB of usable space and 1TB of redundant storage. Now https://brookscipva.blogunteer.com/26339007/detailed-notes-on-raid