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8x 16TB RAID 6 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 8x 16TB in RAID 6. Includes reserve planning for NAS and homelab arrays.

Capacity Snapshot

Raw Capacity

128.00 TB

Usable Capacity

86.40 TB

Fault Tolerance

2 drives

Efficiency

75.0%

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	100.80 TB	1 drive	87.5%
RAID 6	86.40 TB	2 drives	75.0%
RAID 10	57.60 TB	1 drive per mirror pair*	50.0%
RAID-Z1	100.80 TB	1 drive	87.5%
RAID-Z2	86.40 TB	2 drives	75.0%

NAS Cluster Guides

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

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FAQ

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.

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 8x 16TB RAID 6 provide?

This NAS planning scenario estimates 86.40 TB usable after a 10% reserve from 128.00 TB raw.

Why include a 10% reserve when planning NAS capacity?

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