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Brand Focus · Unraid

Unraid 4x 8TB RAID 5 Calculator

Estimate usable capacity, fault tolerance, and efficiency for Unraid NAS users using 4x 8TB in RAID 5.

Capacity Snapshot

Raw Capacity

32.00 TB

Usable Capacity

21.60 TB

Fault Tolerance

1 drive

Efficiency

75.0%

Balanced capacity and redundancy, but rebuild stress can be high on large disks. This scenario applies a 10% filesystem reserve.

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Alternative Mode Comparison

Mode Usable Tolerance Efficiency
RAID 5 21.60 TB 1 drive 75.0%
RAID 6 14.40 TB 2 drives 50.0%
RAID 10 14.40 TB 1 drive per mirror pair* 50.0%
RAID-Z1 21.60 TB 1 drive 75.0%
RAID-Z2 14.40 TB 2 drives 50.0%

Unraid Planning Notes

Unraid users often optimize for incremental growth and flexible disk replacement, where parity planning and usable capacity targets evolve over time rather than all at once.

Brand / Region Glossary

Parity Disk

Dedicated parity disk(s) protecting data disks in the Unraid array model.

Cache Pool

Fast SSD/NVMe pool used for writes and application workloads.

Mover

Scheduled process that migrates data between cache and array tiers.

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

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 5 still practical with 8TB 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 5 tolerate in this setup?

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

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.