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8x 6TB RAID 6 NAS Calculator | Usable TB

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

Capacity Snapshot

Raw Capacity

48.00 TB

Usable Capacity

32.40 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.

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Alternative Mode Comparison

Mode Usable Tolerance Efficiency
RAID 5 37.80 TB 1 drive 87.5%
RAID 6 32.40 TB 2 drives 75.0%
RAID 10 21.60 TB 1 drive per mirror pair* 50.0%
RAID-Z1 37.80 TB 1 drive 87.5%
RAID-Z2 32.40 TB 2 drives 75.0%

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FAQ

Should I optimize this 8-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.

How much usable storage does 8x 6TB RAID 6 provide?

This NAS planning scenario estimates 32.40 TB usable after a 10% reserve from 48.00 TB raw.

Why include a 10% reserve when planning NAS available space?

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

Is RAID 6 still worth deploying with 6TB drives?

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