NAS pSEO Landing
Estimate usable TB, parity overhead, and fault tolerance for 10x 20TB in RAID-Z2. Includes reserve planning for NAS and homelab arrays.
Raw Capacity
200.00 TB
Usable Capacity
144.00 TB
Fault Tolerance
2 drives
Efficiency
80.0%
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 | 162.00 TB | 1 drive | 90.0% |
| RAID 6 | 144.00 TB | 2 drives | 80.0% |
| RAID 10 | 90.00 TB | 1 drive per mirror pair* | 50.0% |
| RAID-Z1 | 162.00 TB | 1 drive | 90.0% |
| RAID-Z2 | 144.00 TB | 2 drives | 80.0% |
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.
This setup can tolerate 2 drives. Real-world survivability depends on mirror placement, rebuild stress, and drive health.
Keeping free space improves filesystem behavior for snapshots, metadata, and write performance. Full arrays often perform worse and rebuild more slowly.