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2x 18TB RAID 1 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 2x 18TB in RAID 1. Includes reserve planning for NAS and homelab arrays.

Capacity Snapshot

Raw Capacity

36.00 TB

Usable Capacity

16.20 TB

Fault Tolerance

1 drives*

Efficiency

50.0%

Strong redundancy but low capacity efficiency. Great for small, critical datasets. This scenario applies a 10% filesystem reserve.

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Alternative Mode Comparison

Mode Usable Tolerance Efficiency
RAID 5 N/A N/A N/A
RAID 6 N/A N/A N/A
RAID 10 N/A N/A N/A
RAID-Z1 N/A N/A N/A
RAID-Z2 N/A N/A N/A

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: 2x 16TB RAID 1 NAS Calculator | Usable TB Next: 2x 20TB RAID 1 NAS Calculator | Usable TB →

FAQ

Can this calculator replace real-world benchmark and rebuild testing?

No. Use this page for pre-purchase sizing, then validate with workload benchmarks, SMART health policy, and a tested restore plan.

How many disk failures can RAID 1 tolerate in this setup?

This setup can tolerate 1 drives*. Real-world survivability depends on mirror placement, rebuild stress, and drive health.

Is RAID 1 still worth deploying 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.

Should I optimize this 2-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.