NAS pSEO Landing
Estimate usable TB, parity overhead, and fault tolerance for 4x 10TB in RAID 10. Includes reserve planning for NAS and homelab arrays.
Raw Capacity
40.00 TB
Usable Capacity
18.00 TB
Fault Tolerance
1 drive per mirror pair*
Efficiency
50.0%
Excellent random I/O and rebuild behavior; capacity is typically 50% of raw. This scenario applies a 10% filesystem reserve.
Run Interactive Calculator →| Mode | Usable | Tolerance | Efficiency |
|---|---|---|---|
| RAID 5 | 27.00 TB | 1 drive | 75.0% |
| RAID 6 | 18.00 TB | 2 drives | 50.0% |
| RAID 10 | 18.00 TB | 1 drive per mirror pair* | 50.0% |
| RAID-Z1 | 27.00 TB | 1 drive | 75.0% |
| RAID-Z2 | 18.00 TB | 2 drives | 50.0% |
It can be practical, but larger drives increase rebuild windows. Validate parity choice and backup policy before committing to the final layout.
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.
This NAS planning scenario estimates 18.00 TB usable after a 10% reserve from 40.00 TB raw.