NAS pSEO Landing
Brand Focus · TrueNAS
Estimate usable TB, parity, and fault tolerance for TrueNAS NAS users using 6x 20TB in RAID-Z1.
Raw Capacity
120.00 TB
Usable Capacity
90.00 TB
Fault Tolerance
1 drive
Efficiency
83.3%
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 | 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% |
TrueNAS and ZFS planners usually care about parity width, scrub cadence, and healthy operating headroom. Capacity is only one part of pool durability.
A virtual device group in ZFS; multiple vdevs form a storage pool.
Background integrity scan that verifies checksums and repairs parity mismatches.
ZFS feature set and planning topic for growing parity groups safely.
For long-lived NAS pools, resiliency first is usually safer. Capacity can be expanded later, while a risky parity choice can force migration sooner.
For TrueNAS users, this NAS planning scenario estimates 90.00 TB usable after a 10% reserve from 120.00 TB raw.
This setup can tolerate 1 drive. Real-world survivability depends on mirror placement, rebuild stress, and drive health.
Keeping free space improves filesystem behavior for snapshots, metadata, and write performance. Full arrays often perform worse and rebuild more slowly.