UK 4x 12TB RAID-Z1 NAS Calculator

Estimate usable TB, parity, and fault tolerance for UK homelab buyers using 4x 12TB in RAID-Z1.

Capacity Snapshot

Raw Capacity

48.00 TB

Usable Capacity

32.40 TB

Fault Tolerance

1 drive

Efficiency

75.0%

ZFS single-parity equivalent of RAID 5; common for smaller homelab pools. This scenario applies a 10% filesystem reserve.

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Alternative Mode Comparison

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

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

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.

How many disk failures can RAID-Z1 tolerate in this setup?

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

Is RAID-Z1 still worth deploying with 12TB drives?

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

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.