QNAP 6x 8TB RAID-Z2 NAS Calculator

Estimate usable TB, parity, and fault tolerance for QNAP NAS users using 6x 8TB in RAID-Z2.

Capacity Snapshot

Raw Capacity

48.00 TB

Usable Capacity

28.80 TB

Fault Tolerance

2 drives

Efficiency

66.7%

Popular TrueNAS default for medium arrays; dual-parity with good safety margin. This scenario applies a 10% filesystem reserve.

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Alternative Mode Comparison

Mode	Usable	Tolerance	Efficiency
RAID 5	36.00 TB	1 drive	83.3%
RAID 6	28.80 TB	2 drives	66.7%
RAID 10	21.60 TB	1 drive per mirror pair*	50.0%
RAID-Z1	36.00 TB	1 drive	83.3%
RAID-Z2	28.80 TB	2 drives	66.7%

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.

• Model around mixed workloads: media throughput plus VM random I/O.
• Reserve enough headroom so thin-provisioned services do not overrun the array.
• When in doubt, prioritize safer parity for arrays above 6 drives.

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.

NAS Cluster Guides

NAS Hub RAID Level Compare RAID Capacity Matrix Planning Quick Sheet RAID Selector NAS FAQ

Related Long-Tail Calculators

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Sequential Long-Tail Navigation

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FAQ

How many disk failures can RAID-Z2 tolerate in this setup?

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

How much usable storage does 6x 8TB RAID-Z2 provide?

For QNAP users, this NAS planning scenario estimates 28.80 TB usable after a 10% reserve from 48.00 TB raw.

Should I optimize this 6-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.

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.