NAS pSEO Landing
Estimate usable TB, parity overhead, and fault tolerance for 12x 4TB in RAID 1. Includes reserve planning for NAS and homelab arrays.
Raw Capacity
48.00 TB
Usable Capacity
3.60 TB
Fault Tolerance
11 drives*
Efficiency
8.3%
Strong redundancy but low capacity efficiency. Great for small, critical datasets. This scenario applies a 10% filesystem reserve.
Run Interactive Calculator →| Mode | Usable | Tolerance | Efficiency |
|---|---|---|---|
| RAID 5 | 39.60 TB | 1 drive | 91.7% |
| RAID 6 | 36.00 TB | 2 drives | 83.3% |
| RAID 10 | 21.60 TB | 1 drive per mirror pair* | 50.0% |
| RAID-Z1 | 39.60 TB | 1 drive | 91.7% |
| RAID-Z2 | 36.00 TB | 2 drives | 83.3% |
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.
This setup can tolerate 11 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.