UK 8x 8TB RAID-Z2 NAS Calculator

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

Capacity Snapshot

Raw Capacity

64.00 TB

Usable Capacity

43.20 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	50.40 TB	1 drive	87.5%
RAID 6	43.20 TB	2 drives	75.0%
RAID 10	28.80 TB	1 drive per mirror pair*	50.0%
RAID-Z1	50.40 TB	1 drive	87.5%
RAID-Z2	43.20 TB	2 drives	75.0%

UK Buyer Context

UK homelab planners commonly balance higher per-drive pricing with power and chassis constraints, so efficient but resilient layouts become more valuable.

• Model dual-parity options early if rebuild time is a concern.
• Include reserve headroom to avoid running pools at high fill percentages.

Brand / Region Glossary

Power Budget

Expected always-on energy usage cost factored into NAS layout decisions.

Rebuild Window

Estimated time exposure while replacing a failed drive and restoring parity.

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

Is RAID-Z2 still practical with 8TB drives?

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

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.

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-Z2 tolerate in this setup?

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