NAS pSEO Landing
Estimate usable TB, parity overhead, and fault tolerance for 8x 16TB in RAID-Z2. Includes reserve planning for NAS and homelab arrays.
Raw Capacity
128.00 TB
Usable Capacity
86.40 TB
Fault Tolerance
2 drives
Efficiency
75.0%
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 | 100.80 TB | 1 drive | 87.5% |
| RAID 6 | 86.40 TB | 2 drives | 75.0% |
| RAID 10 | 57.60 TB | 1 drive per mirror pair* | 50.0% |
| RAID-Z1 | 100.80 TB | 1 drive | 87.5% |
| RAID-Z2 | 86.40 TB | 2 drives | 75.0% |
No. Use this page for pre-purchase sizing, then validate with workload benchmarks, SMART health policy, and a tested restore plan.
For long-lived NAS pools, resiliency first is usually safer. Capacity can be expanded later, while a risky parity choice can force migration sooner.
It can be practical, but larger drives increase rebuild windows. Validate parity choice and backup policy before committing to the final layout.
This setup can tolerate 2 drives. Real-world survivability depends on mirror placement, rebuild stress, and drive health.