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4x 10TB RAID 1 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 4x 10TB in RAID 1. Includes reserve planning for NAS and homelab arrays.

Capacity Snapshot

Raw Capacity

40.00 TB

Usable Capacity

9.00 TB

Fault Tolerance

3 drives*

Efficiency

25.0%

Strong redundancy but low capacity efficiency. Great for small, critical datasets. This scenario applies a 10% filesystem reserve.

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Alternative Mode Comparison

Mode Usable Tolerance Efficiency
RAID 5 27.00 TB 1 drive 75.0%
RAID 6 18.00 TB 2 drives 50.0%
RAID 10 18.00 TB 1 drive per mirror pair* 50.0%
RAID-Z1 27.00 TB 1 drive 75.0%
RAID-Z2 18.00 TB 2 drives 50.0%

NAS Cluster Guides

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

Related Long-Tail Calculators

2x 4TB RAID 1 2x 6TB RAID 1 2x 8TB RAID 1 2x 10TB RAID 1 2x 12TB RAID 1 2x 14TB RAID 1 2x 16TB RAID 1 2x 18TB RAID 1 2x 20TB RAID 1 3x 4TB RAID 1 3x 4TB RAID 5 3x 4TB RAID-Z1 3x 6TB RAID 1 3x 6TB RAID 5 3x 6TB RAID-Z1 3x 8TB RAID 1

Sequential Long-Tail Navigation

← Previous: 4x 8TB RAID-Z2 NAS Calculator | Usable TB Next: 4x 10TB RAID 5 NAS Calculator | Usable TB →

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 1 tolerate in this setup?

This setup can tolerate 3 drives*. Real-world survivability depends on mirror placement, rebuild stress, and drive health.

Should I optimize this 4-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 4x 10TB RAID 1 provide?

This NAS planning scenario estimates 9.00 TB usable after a 10% reserve from 40.00 TB raw.