NAS pSEO Landing
Estimate usable TB, parity overhead, and fault tolerance for 4x 14TB in RAID-Z2. Includes reserve planning for NAS and homelab arrays.
Raw Capacity
56.00 TB
Usable Capacity
25.20 TB
Fault Tolerance
2 drives
Efficiency
50.0%
Popular TrueNAS default for medium arrays; dual-parity with good safety margin. This scenario applies a 10% filesystem reserve.
Run Interactive Calculator →| Mode | Usable | Tolerance | Efficiency |
|---|---|---|---|
| RAID 5 | 37.80 TB | 1 drive | 75.0% |
| RAID 6 | 25.20 TB | 2 drives | 50.0% |
| RAID 10 | 25.20 TB | 1 drive per mirror pair* | 50.0% |
| RAID-Z1 | 37.80 TB | 1 drive | 75.0% |
| RAID-Z2 | 25.20 TB | 2 drives | 50.0% |
For long-lived NAS pools, resiliency first is usually safer. Capacity can be expanded later, while a risky parity choice can force migration sooner.
This setup can tolerate 2 drives. Real-world survivability depends on mirror placement, rebuild stress, and drive health.
It can be practical, but larger drives increase rebuild windows. Validate parity choice and backup policy before committing to the final layout.
This NAS planning scenario estimates 25.20 TB usable after a 10% reserve from 56.00 TB raw.