Consistent inputs
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Citation asset
NAS RAID Capacity Matrix
A reference matrix for architecture proposals and NAS purchase planning. All levels are compared using the same drive baselines and reserve policy.
Reference assumptions
Consistent baselines, fair comparison
The matrix compares 4x 8TB and 8x 12TB arrays with the same 10% reserve, so capacity differences come from RAID behavior.
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. |
Reference trust layer
How to use this matrix without over-trusting it
The matrix is designed to be citation-friendly, but final storage decisions still need scenario-specific validation.
Citation boundary
The matrix explains capacity, not total reliability
Usable TB and tolerance are visible here, while backup, restore testing, controller behavior, and drive health still need separate validation.Decision route
Reference data links back to practical planning pages
Use the matrix to shortlist candidates, then move to the selector or calculator before buying hardware.Method
How this page makes decisions
Baselines 4x 8TB and 8x 12TB arrays are calculated with the same 10% reserve.
Metrics Usable TB, tolerance, and efficiency are shown for each valid RAID level.
Invalid states Modes that do not fit the drive count are explicitly marked instead of estimated.
Next step The selector and calculator convert matrix findings into a specific build path.
Pre-action checks
Matrix review checklist
- Use the same reserve percentage when comparing candidate layouts.
- Check whether the chosen mode is valid for the planned drive count.
- Compare capacity gain against failure tolerance loss.
- Validate rebuild and restore expectations before procurement.
- Open the calculator for your exact drive size and reserve policy.
This page is designed as a planning aid, not a final professional review. Product and service links may be neutral category searches until disclosed partner links are ready.
DisclosureNAS cluster navigation