NAS pSEO Landing
Estimate usable TB, parity overhead, and fault tolerance for 4x 20TB in RAID-Z1. Includes reserve planning for NAS and homelab arrays.
Raw Capacity
80.00 TB
Usable Capacity
54.00 TB
Fault Tolerance
1 drive
Efficiency
75.0%
ZFS single-parity equivalent of RAID 5; common for smaller homelab pools. This scenario applies a 10% filesystem reserve.
Run Interactive Calculator →| Mode | Usable | Tolerance | Efficiency |
|---|---|---|---|
| RAID 5 | 54.00 TB | 1 drive | 75.0% |
| RAID 6 | 36.00 TB | 2 drives | 50.0% |
| RAID 10 | 36.00 TB | 1 drive per mirror pair* | 50.0% |
| RAID-Z1 | 54.00 TB | 1 drive | 75.0% |
| RAID-Z2 | 36.00 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.
For long-lived NAS pools, resiliency first is usually safer. Capacity can be expanded later, while a risky parity choice can force migration sooner.
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.