Week 5 Citation Asset
NAS RAID Capacity Matrix
This matrix is built for direct reference in architecture proposals. All levels are compared using the same drive baselines and reserve policy.
Directly Quotable Conclusions
- For medium and large arrays, dual-parity layouts (RAID 6 / RAID-Z2) usually offer the best safety-to-capacity balance.
- RAID 10 provides strong rebuild behavior but gives up substantial usable capacity.
- RAID 5 and RAID-Z1 can maximize usable space in smaller arrays, but risk profile increases with larger drive sizes.
- All matrix values here apply a consistent 10% reserve policy for fair comparison.
RAID Level Matrix
| Mode | 4x 8TB (entry homelab) | 8x 12TB (growing NAS) | Planning Note |
|---|---|---|---|
| RAID 1 | Usable: 7.2 TB Tolerance: 3 drives* Efficiency: 25.0% | Usable: 10.8 TB Tolerance: 7 drives* Efficiency: 12.5% | High redundancy with low capacity efficiency. |
| RAID 5 | Usable: 21.6 TB Tolerance: 1 drive Efficiency: 75.0% | Usable: 75.6 TB Tolerance: 1 drive Efficiency: 87.5% | Balanced capacity for smaller arrays, but rebuild stress can rise on large drives. |
| RAID 6 | Usable: 14.4 TB Tolerance: 2 drives Efficiency: 50.0% | Usable: 64.8 TB Tolerance: 2 drives Efficiency: 75.0% | Dual parity improves resilience for medium and large arrays. |
| RAID 10 | Usable: 14.4 TB Tolerance: 1 drive per mirror pair* Efficiency: 50.0% | Usable: 43.2 TB Tolerance: 1 drive per mirror pair* Efficiency: 50.0% | Strong random I/O and rebuild behavior; capacity overhead is significant. |
| RAID-Z1 | Usable: 21.6 TB Tolerance: 1 drive Efficiency: 75.0% | Usable: 75.6 TB Tolerance: 1 drive Efficiency: 87.5% | Single parity option commonly used for smaller ZFS pools. |
| RAID-Z2 | Usable: 14.4 TB Tolerance: 2 drives Efficiency: 50.0% | Usable: 64.8 TB Tolerance: 2 drives Efficiency: 75.0% | Dual parity ZFS baseline for safer medium-to-large pools. |
| RAID-Z3 | Not valid for this drive count | Usable: 54.0 TB Tolerance: 3 drives Efficiency: 62.5% | Triple parity for large pools with long rebuild windows. |