Calculate usable capacity across RAID 0, 1, 5, 6 and 10 configurations.
RAID levels trade capacity for redundancy. RAID 0 offers full capacity but zero fault tolerance. RAID 1 mirrors all data (50% efficiency for 2 drives). RAID 5 uses one drive's worth for distributed parity (n-1 efficiency). RAID 6 uses two drives for double parity. RAID 10 stripes across mirror pairs (50% efficiency).
RAID 5 usable capacity
usable = (drives - 1) * drive_size
RAID 6 usable capacity
usable = (drives - 2) * drive_size
RAID 5 balances capacity and protection for most workloads. RAID 6 is preferred for large arrays (>4 drives) where rebuild times are long enough to risk a second failure. RAID 10 is best for write-intensive workloads needing both performance and redundancy. RAID 0 is only appropriate when data loss is acceptable.
RAID protects against drive failure only. It cannot protect against accidental deletion, corruption, ransomware, controller failure, or disasters affecting the entire array. Backups protect against all of these scenarios.