NAS pSEO Landing
Estimate usable TB, parity overhead, and fault tolerance for 12x 18TB in RAID 1. Includes reserve planning for NAS and homelab arrays.
Raw Capacity
216.00 TB
Usable Capacity
16.20 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 | 178.20 TB | 1 drive | 91.7% |
| RAID 6 | 162.00 TB | 2 drives | 83.3% |
| RAID 10 | 97.20 TB | 1 drive per mirror pair* | 50.0% |
| RAID-Z1 | 178.20 TB | 1 drive | 91.7% |
| RAID-Z2 | 162.00 TB | 2 drives | 83.3% |
This NAS planning scenario estimates 16.20 TB usable after a 10% reserve from 216.00 TB raw.
Keeping free space improves filesystem behavior for snapshots, metadata, and write performance. Full arrays often perform worse and rebuild more slowly.
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.