← NAS & RAID Calculator

NAS pSEO Landing

12x 18TB RAID-Z2 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 12x 18TB in RAID-Z2. Includes reserve planning for NAS and homelab arrays.

Capacity Snapshot

Raw Capacity

216.00 TB

Usable Capacity

162.00 TB

Fault Tolerance

2 drives

Efficiency

83.3%

Popular TrueNAS default for medium arrays; dual-parity with good safety margin. This scenario applies a 10% filesystem reserve.

Run Interactive Calculator →

Alternative Mode Comparison

Mode Usable Tolerance Efficiency
RAID 5 178.20 TB 1 drive 91.7%
RAID 6 162.00 TB 2 drives 83.3%
RAID 10 97.20 TB 1 drive per mirror pair* 50.0%
RAID-Z1 178.20 TB 1 drive 91.7%
RAID-Z2 162.00 TB 2 drives 83.3%

NAS Cluster Guides

NAS Hub RAID Level Compare RAID Capacity Matrix Planning Quick Sheet RAID Selector NAS FAQ

Related Long-Tail Calculators

2x 4TB RAID 1 2x 6TB RAID 1 2x 8TB RAID 1 2x 10TB RAID 1 2x 12TB RAID 1 2x 14TB RAID 1 2x 16TB RAID 1 2x 18TB RAID 1 2x 20TB RAID 1 3x 4TB RAID 1 3x 4TB RAID 5 3x 4TB RAID-Z1 3x 6TB RAID 1 3x 6TB RAID 5 3x 6TB RAID-Z1 3x 8TB RAID 1

Sequential Long-Tail Navigation

← Previous: 12x 18TB RAID-Z1 NAS Calculator | Usable TB Next: 12x 20TB RAID 1 NAS Calculator | Usable TB →

FAQ

How much real-world usable storage does 12x 18TB RAID-Z2 provide?

This NAS planning scenario estimates 162.00 TB usable after a 10% reserve from 216.00 TB raw.

How many disk failures can RAID-Z2 tolerate in this setup?

This setup can tolerate 2 drives. Real-world survivability depends on mirror placement, rebuild stress, and drive health.

Should I optimize this 12-drive plan for storage headroom or resiliency first?

For long-lived NAS pools, resiliency first is usually safer. Capacity can be expanded later, while a risky parity choice can force migration sooner.

Is RAID-Z2 still practical with 18TB drives?

It can be practical, but larger drives increase rebuild windows. Validate parity choice and backup policy before committing to the final layout.