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5x 18TB RAID 6 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 5x 18TB in RAID 6. Includes reserve planning for NAS and homelab arrays.

Capacity Snapshot

Raw Capacity

90.00 TB

Usable Capacity

48.60 TB

Fault Tolerance

2 drives

Efficiency

60.0%

Safer for larger arrays with dual parity, at the cost of one extra parity disk. This scenario applies a 10% filesystem reserve.

Run Interactive Calculator →

Alternative Mode Comparison

Mode Usable Tolerance Efficiency
RAID 5 64.80 TB 1 drive 80.0%
RAID 6 48.60 TB 2 drives 60.0%
RAID 10 N/A N/A N/A
RAID-Z1 64.80 TB 1 drive 80.0%
RAID-Z2 48.60 TB 2 drives 60.0%

NAS Cluster Guides

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

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Sequential Long-Tail Navigation

← Previous: 5x 18TB RAID 5 NAS Calculator | Usable TB Next: 5x 18TB RAID-Z1 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 6 tolerate in this setup?

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

How much effective storage does 5x 18TB RAID 6 provide?

This NAS planning scenario estimates 48.60 TB usable after a 10% reserve from 90.00 TB raw.

Why include a 10% reserve when planning NAS storage headroom?

Keeping free space improves filesystem behavior for snapshots, metadata, and write performance. Full arrays often perform worse and rebuild more slowly.