NAS pSEO Landing
Estimate usable TB, parity overhead, and fault tolerance for 6x 18TB in RAID-Z2. Includes reserve planning for NAS and homelab arrays.
Raw Capacity
108.00 TB
Usable Capacity
64.80 TB
Fault Tolerance
2 drives
Efficiency
66.7%
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 | 81.00 TB | 1 drive | 83.3% |
| RAID 6 | 64.80 TB | 2 drives | 66.7% |
| RAID 10 | 48.60 TB | 1 drive per mirror pair* | 50.0% |
| RAID-Z1 | 81.00 TB | 1 drive | 83.3% |
| RAID-Z2 | 64.80 TB | 2 drives | 66.7% |
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.
For long-lived NAS pools, resiliency first is usually safer. Capacity can be expanded later, while a risky parity choice can force migration sooner.
No. Use this page for pre-purchase sizing, then validate with workload benchmarks, SMART health policy, and a tested restore plan.