NAS pSEO Landing
Estimate usable TB, parity overhead, and fault tolerance for 4x 12TB in RAID 10. Includes reserve planning for NAS and homelab arrays.
Raw Capacity
48.00 TB
Usable Capacity
21.60 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 | 32.40 TB | 1 drive | 75.0% |
| RAID 6 | 21.60 TB | 2 drives | 50.0% |
| RAID 10 | 21.60 TB | 1 drive per mirror pair* | 50.0% |
| RAID-Z1 | 32.40 TB | 1 drive | 75.0% |
| RAID-Z2 | 21.60 TB | 2 drives | 50.0% |
Keeping free space improves filesystem behavior for snapshots, metadata, and write performance. Full arrays often perform worse and rebuild more slowly.
This NAS planning scenario estimates 21.60 TB usable after a 10% reserve from 48.00 TB raw.
No. Use this page for pre-purchase sizing, then validate with workload benchmarks, SMART health policy, and a tested restore plan.
For long-lived NAS pools, resiliency first is usually safer. Capacity can be expanded later, while a risky parity choice can force migration sooner.