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3x 10TB RAID 1 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 3x 10TB in RAID 1. Includes reserve planning for NAS and homelab arrays.

Capacity Snapshot

Raw Capacity

30.00 TB

Usable Capacity

9.00 TB

Fault Tolerance

2 drives*

Efficiency

33.3%

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 18.00 TB 1 drive 66.7%
RAID 6 N/A N/A N/A
RAID 10 N/A N/A N/A
RAID-Z1 18.00 TB 1 drive 66.7%
RAID-Z2 N/A N/A N/A

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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.

Should I optimize this 3-drive plan for available space 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.

Is RAID 1 still worth deploying with 10TB 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 1 tolerate in this setup?

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