US 8x 16TB RAID-Z2 NAS Calculator

Estimate usable TB, parity, and fault tolerance for US homelab buyers using 8x 16TB in RAID-Z2.

Capacity Snapshot

Raw Capacity

128.00 TB

Usable Capacity

86.40 TB

Fault Tolerance

2 drives

Efficiency

75.0%

Popular TrueNAS default for medium arrays; dual-parity with good safety margin. This scenario applies a 10% filesystem reserve.

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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%

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

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Sequential Long-Tail Navigation

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FAQ

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.

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.

Is RAID-Z2 still worth deploying with 16TB drives?

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

How many disk failures can RAID-Z2 tolerate in this setup?

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