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2x 4TB RAID 1 Calculator

Estimate usable capacity, fault tolerance, and efficiency for 2x 4TB in RAID 1 with reserve best practices.

Capacity Snapshot

Raw Capacity

8.00 TB

Usable Capacity

3.60 TB

Fault Tolerance

1 drives*

Efficiency

50.0%

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 N/A N/A N/A
RAID 6 N/A N/A N/A
RAID 10 N/A N/A N/A
RAID-Z1 N/A N/A N/A
RAID-Z2 N/A N/A N/A

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

FAQ

How much real-world usable storage does 2x 4TB RAID 1 provide?

This NAS planning scenario estimates 3.60 TB usable after a 10% reserve from 8.00 TB raw.

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.

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.

Should I optimize this 2-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.