NAS planning example
Estimate usable TB, parity overhead, and fault tolerance for 4x 4TB in RAID 10. Includes reserve planning for NAS and homelab arrays.
Planning route
Use this worked example as a numeric starting point, then validate the RAID choice, capacity reserve, hardware plan, and backup path.
Editorial method
The capacity model makes drive count, drive size, RAID layout, and reserve visible. It is a planning aid: it does not predict exact performance, rebuild duration, hardware compatibility, or the probability of data loss for a specific system.
Last reviewed: July 10, 2026. Product links remain neutral category searches until a partner relationship and page-level disclosure are in place.
Raw Capacity
16.00 TB
Usable Capacity
7.20 TB
Fault Tolerance
1 drive per mirror pair*
Efficiency
50.0%
Excellent random I/O and rebuild behavior; capacity is typically 50% of raw. This scenario applies a 10% filesystem reserve.
Run Interactive Calculator →| Mode | Usable | Tolerance | Efficiency |
|---|---|---|---|
| RAID 5 | 10.80 TB | 1 drive | 75.0% |
| RAID 6 | 7.20 TB | 2 drives | 50.0% |
| RAID 10 | 7.20 TB | 1 drive per mirror pair* | 50.0% |
| RAID-Z1 | 10.80 TB | 1 drive | 75.0% |
| RAID-Z2 | 7.20 TB | 2 drives | 50.0% |
NAS cluster navigation
Related long-tail calculators
Sequential long-tail navigation
FAQ
This NAS planning scenario estimates 7.20 TB usable after a 10% reserve from 16.00 TB raw.
For long-lived NAS pools, resiliency first is usually safer. Capacity can be expanded later, while a risky parity choice can force migration sooner.
It can be practical, but larger drives increase rebuild windows. Validate parity choice and backup policy before committing to the final layout.
No. Use this page for pre-purchase sizing, then validate with workload benchmarks, SMART health policy, and a tested restore plan.