Storage
RAID Calculator
Raw vs usable capacity, parity overhead and fault tolerance — computed on the server from your exact inputs.
Capacity — RAID 5, 4 × 4.00 TB
- Raw capacity
- 16.0 TB
- Usable capacity
- 12.0 TB
- Parity / mirror overhead
- 4.00 TB
- Efficiency
- 75.0 %
usable 12.0 TB+ parity 4.00 TB
Fault tolerance
Survives up to 1 drive failure
Single parity — good balance; rebuild time matters on big drives
Rebuild math
After a failure, the surviving drives rewrite the missing blocks. For RAID 5: up to 1 failure until the next drive dies — replace failed drives promptly. Large-capacity disks (8 TB+) rebuild slowly; consider RAID 6 for arrays above eight drives.
Numbers are instantaneous-geometry estimates; filesystem overhead (ZFS, XFS, ext4), hot spares and 512e/4Kn alignment are not included. Always leave headroom; never fill an array past 80 %.