NAS pSEO Landing
Estimate usable TB, parity overhead, and fault tolerance for 8x 4TB in RAID 5. Includes reserve planning for NAS and homelab arrays.
Raw Capacity
32.00 TB
Usable Capacity
25.20 TB
Fault Tolerance
1 drive
Efficiency
87.5%
Balanced capacity and redundancy, but rebuild stress can be high on large disks. This scenario applies a 10% filesystem reserve.
Run Interactive Calculator →| Mode | Usable | Tolerance | Efficiency |
|---|---|---|---|
| RAID 5 | 25.20 TB | 1 drive | 87.5% |
| RAID 6 | 21.60 TB | 2 drives | 75.0% |
| RAID 10 | 14.40 TB | 1 drive per mirror pair* | 50.0% |
| RAID-Z1 | 25.20 TB | 1 drive | 87.5% |
| RAID-Z2 | 21.60 TB | 2 drives | 75.0% |
No. Use this page for pre-purchase sizing, then validate with workload benchmarks, SMART health policy, and a tested restore plan.
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 setup can tolerate 1 drive. Real-world survivability depends on mirror placement, rebuild stress, and drive health.