NAS pSEO Landing
Region Focus · UK
Estimate usable TB, parity, and fault tolerance for UK homelab buyers using 6x 20TB in RAID-Z2.
Raw Capacity
120.00 TB
Usable Capacity
72.00 TB
Fault Tolerance
2 drives
Efficiency
66.7%
Popular TrueNAS default for medium arrays; dual-parity with good safety margin. This scenario applies a 10% filesystem reserve.
Run Interactive Calculator →| Mode | Usable | Tolerance | Efficiency |
|---|---|---|---|
| RAID 5 | 90.00 TB | 1 drive | 83.3% |
| RAID 6 | 72.00 TB | 2 drives | 66.7% |
| RAID 10 | 54.00 TB | 1 drive per mirror pair* | 50.0% |
| RAID-Z1 | 90.00 TB | 1 drive | 83.3% |
| RAID-Z2 | 72.00 TB | 2 drives | 66.7% |
UK homelab planners commonly balance higher per-drive pricing with power and chassis constraints, so efficient but resilient layouts become more valuable.
Expected always-on energy usage cost factored into NAS layout decisions.
Estimated time exposure while replacing a failed drive and restoring parity.
For long-lived NAS pools, resiliency first is usually safer. Capacity can be expanded later, while a risky parity choice can force migration sooner.
Keeping free space improves filesystem behavior for snapshots, metadata, and write performance. Full arrays often perform worse and rebuild more slowly.
It can be practical, but larger drives increase rebuild windows. Validate parity choice and backup policy before committing to the final layout.
This setup can tolerate 2 drives. Real-world survivability depends on mirror placement, rebuild stress, and drive health.