RAID

Redundant Array of Independent Disks

RAID 0 - striping, no data protection, only increase storage/retrieval speed
RAID 1 - mirroring, 1/2 of usable space
RAID 5 - parity, 3+ drives, n-1 disks of usable space
RAID 6 - 2 parities, 4+ drives, n-2 disks of usable space
RAID 10 - RAID 0 + RAID 1, 1/2 of usable space

https://www.youtube.com/watch?v=PP0iQs8qBNU