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12x 20TB RAID 10 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 12x 20TB in RAID 10. Includes reserve planning for NAS and homelab arrays.

Capacity Snapshot

Raw Capacity

240.00 TB

Usable Capacity

108.00 TB

Fault Tolerance

1 drive per mirror pair*

Efficiency

50.0%

Excellent random I/O and rebuild behavior; capacity is typically 50% of raw. This scenario applies a 10% filesystem reserve.

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Alternative Mode Comparison

Mode Usable Tolerance Efficiency
RAID 5 198.00 TB 1 drive 91.7%
RAID 6 180.00 TB 2 drives 83.3%
RAID 10 108.00 TB 1 drive per mirror pair* 50.0%
RAID-Z1 198.00 TB 1 drive 91.7%
RAID-Z2 180.00 TB 2 drives 83.3%

NAS Cluster Guides

NAS Hub RAID Level Compare RAID Capacity Matrix Planning Quick Sheet RAID Selector NAS FAQ

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Sequential Long-Tail Navigation

← Previous: 12x 20TB RAID 6 NAS Calculator | Usable TB Next: 12x 20TB RAID-Z1 NAS Calculator | Usable TB →

FAQ

Should I optimize this 12-drive plan for capacity 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.

How much usable storage does 12x 20TB RAID 10 provide?

This NAS planning scenario estimates 108.00 TB usable after a 10% reserve from 240.00 TB raw.

How many disk failures can RAID 10 tolerate in this setup?

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

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.