NAS pSEO Landing
Estimate usable TB, parity overhead, and fault tolerance for 8x 18TB in RAID 1. Includes reserve planning for NAS and homelab arrays.
Raw Capacity
144.00 TB
Usable Capacity
16.20 TB
Fault Tolerance
7 drives*
Efficiency
12.5%
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 | 113.40 TB | 1 drive | 87.5% |
| RAID 6 | 97.20 TB | 2 drives | 75.0% |
| RAID 10 | 64.80 TB | 1 drive per mirror pair* | 50.0% |
| RAID-Z1 | 113.40 TB | 1 drive | 87.5% |
| RAID-Z2 | 97.20 TB | 2 drives | 75.0% |
Keeping free space improves filesystem behavior for snapshots, metadata, and write performance. Full arrays often perform worse and rebuild more slowly.
No. Use this page for pre-purchase sizing, then validate with workload benchmarks, SMART health policy, and a tested restore plan.
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.