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6x 18TB RAID 10 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 6x 18TB in RAID 10. Includes reserve planning for NAS and homelab arrays.

Capacity Snapshot

Raw Capacity

108.00 TB

Usable Capacity

48.60 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.

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Alternative Mode Comparison

Mode Usable Tolerance Efficiency
RAID 5 81.00 TB 1 drive 83.3%
RAID 6 64.80 TB 2 drives 66.7%
RAID 10 48.60 TB 1 drive per mirror pair* 50.0%
RAID-Z1 81.00 TB 1 drive 83.3%
RAID-Z2 64.80 TB 2 drives 66.7%

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FAQ

Should I optimize this 6-drive plan for capacity 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.

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 much real-world usable storage does 6x 18TB RAID 10 provide?

This NAS planning scenario estimates 48.60 TB usable after a 10% reserve from 108.00 TB raw.

How many disk failures can RAID 10 tolerate in this setup?

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