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QNAP 4x 8TB RAID 5 Calculator

Estimate usable capacity, fault tolerance, and efficiency for QNAP 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%

QNAP Planning Notes

QNAP buyers often compare capacity efficiency against service consolidation needs, where VM storage, containers, and media serving all compete for IOPS and free space.

Brand / Region Glossary

Qtier

QNAP auto-tiering system that moves hot and cold data across storage classes.

Storage & Snapshots

QTS module for RAID pool management, volume control, and snapshots.

Thin Provisioning

Allocates logical space first and consumes physical capacity over time.

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 4x 8TB RAID 5 provide?

For QNAP users, this NAS planning scenario estimates 21.60 TB usable after a 10% reserve from 32.00 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.

Should I optimize this 4-drive plan for storage headroom 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.

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.