RAID Storage Calculator
Calculate usable storage and fault tolerance for RAID 0, 1, 5, 6, and 10.
Compare all five configurations side by side for any number of drives.
RAID Storage Calculator
RAID (Redundant Array of Independent Disks) combines multiple drives into one logical unit. Different RAID levels trade usable storage against redundancy and performance.
RAID Level Summary:
| Level | Min Drives | Usable Storage | Fault Tolerance | Use Case |
|---|---|---|---|---|
| RAID 0 | 2 | 100% of all drives | None — any failure = data loss | Speed only |
| RAID 1 | 2 | 50% (mirrored pair) | 1 drive | Simple mirroring |
| RAID 5 | 3 | (N−1) drives | 1 drive | Balance of space + safety |
| RAID 6 | 4 | (N−2) drives | 2 drives | Higher safety |
| RAID 10 | 4 (even) | 50% | 1 per mirrored pair | Speed + redundancy |
Formulas:
RAID 0: Usable = N × Capacity
RAID 1: Usable = Capacity (regardless of how many drives — all are mirrors)
RAID 5: Usable = (N − 1) × Capacity
RAID 6: Usable = (N − 2) × Capacity
RAID 10: Usable = (N / 2) × Capacity
Overhead percentage:
Overhead % = (1 − Usable / Total Raw) × 100
Choosing a RAID level:
Use RAID 0 only for non-critical data where speed matters. Use RAID 1 for simple two-disk mirroring (boot drives, critical single servers). Use RAID 5 for NAS and small servers — good balance of storage efficiency and one-drive tolerance. Use RAID 6 when downtime during a rebuild is unacceptable. Use RAID 10 for high-performance databases — fast reads/writes with full redundancy.
RAID is not a backup:
RAID protects against a drive failure. It does not protect against accidental deletion, ransomware, or controller failure. Always maintain a separate backup copy of important data.