NAS planning example
Estimate usable TB, parity overhead, and fault tolerance for 12x 6TB in RAID-Z1. 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
72.00 TB
Usable Capacity
59.40 TB
Fault Tolerance
1 drive
Efficiency
91.7%
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 | 59.40 TB | 1 drive | 91.7% |
| RAID 6 | 54.00 TB | 2 drives | 83.3% |
| RAID 10 | 32.40 TB | 1 drive per mirror pair* | 50.0% |
| RAID-Z1 | 59.40 TB | 1 drive | 91.7% |
| RAID-Z2 | 54.00 TB | 2 drives | 83.3% |
NAS cluster navigation
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Sequential long-tail navigation
FAQ
Keeping free space improves filesystem behavior for snapshots, metadata, and write performance. Full arrays often perform worse and rebuild more slowly.
This setup can tolerate 1 drive. Real-world survivability depends on mirror placement, rebuild stress, and drive health.
This NAS planning scenario estimates 59.40 TB usable after a 10% reserve from 72.00 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.