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3x 4TB RAID 1 Calculator

Estimate usable capacity, fault tolerance, and efficiency for 3x 4TB in RAID 1 with reserve best practices.

Capacity Snapshot

Raw Capacity

12.00 TB

Usable Capacity

3.60 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.

Run Interactive Calculator →

Alternative Mode Comparison

Mode Usable Tolerance Efficiency
RAID 5 7.20 TB 1 drive 66.7%
RAID 6 N/A N/A N/A
RAID 10 N/A N/A N/A
RAID-Z1 7.20 TB 1 drive 66.7%
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 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.

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.

Is RAID 1 still practical with 4TB drives?

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

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.