UK 8x 20TB RAID 5 NAS Calculator

Estimate usable TB, parity, and fault tolerance for UK homelab buyers using 8x 20TB in RAID 5.

Capacity Snapshot

Raw Capacity

160.00 TB

Usable Capacity

126.00 TB

Fault Tolerance

1 drive

Efficiency

87.5%

Balanced capacity and redundancy, but rebuild stress can be high on large disks. 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%

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

How much real-world usable storage does 8x 20TB RAID 5 provide?

For UK homelab buyers, this NAS planning scenario estimates 126.00 TB usable after a 10% reserve from 160.00 TB raw.

Is RAID 5 still worth deploying 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 many disk failures can RAID 5 tolerate in this setup?

This setup can tolerate 1 drive. Real-world survivability depends on mirror placement, rebuild stress, and drive health.

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.