US 8x 20TB RAID 6 NAS Calculator

Estimate usable TB, parity, and fault tolerance for US homelab buyers using 8x 20TB in RAID 6.

Capacity Snapshot

Raw Capacity

160.00 TB

Usable Capacity

108.00 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	126.00 TB	1 drive	87.5%
RAID 6	108.00 TB	2 drives	75.0%
RAID 10	72.00 TB	1 drive per mirror pair*	50.0%
RAID-Z1	126.00 TB	1 drive	87.5%
RAID-Z2	108.00 TB	2 drives	75.0%

US Buyer Context

US buyers often evaluate frequent pricing swings and promo cycles. Capacity planning should account for staged purchases instead of one-time all-disk upgrades.

• Use parity layouts that remain valid during phased expansions.
• Compare total usable-per-dollar across multiple disk sizes, not only one SKU.

Brand / Region Glossary

Cost-per-Usable-TB

Planning metric that compares real usable capacity after reserve and parity.

Promo Window

Seasonal pricing period used for phased drive purchasing strategies.

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

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FAQ

Is RAID 6 still practical with 20TB drives?

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

How much effective storage does 8x 20TB RAID 6 provide?

For US homelab buyers, this NAS planning scenario estimates 108.00 TB usable after a 10% reserve from 160.00 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.

Should I optimize this 8-drive plan for available space 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.