NAS pSEO Landing
Estimate usable TB, parity overhead, and fault tolerance for 4x 8TB in RAID 1. Includes reserve planning for NAS and homelab arrays.
Raw Capacity
32.00 TB
Usable Capacity
7.20 TB
Fault Tolerance
3 drives*
Efficiency
25.0%
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 | 21.60 TB | 1 drive | 75.0% |
| RAID 6 | 14.40 TB | 2 drives | 50.0% |
| RAID 10 | 14.40 TB | 1 drive per mirror pair* | 50.0% |
| RAID-Z1 | 21.60 TB | 1 drive | 75.0% |
| RAID-Z2 | 14.40 TB | 2 drives | 50.0% |
This setup can tolerate 3 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.
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.