QNAP 10x 20TB RAID-Z2 NAS Calculator

Estimate usable TB, parity, and fault tolerance for QNAP NAS users using 10x 20TB in RAID-Z2.

Capacity Snapshot

Raw Capacity

200.00 TB

Usable Capacity

144.00 TB

Fault Tolerance

2 drives

Efficiency

80.0%

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	162.00 TB	1 drive	90.0%
RAID 6	144.00 TB	2 drives	80.0%
RAID 10	90.00 TB	1 drive per mirror pair*	50.0%
RAID-Z1	162.00 TB	1 drive	90.0%
RAID-Z2	144.00 TB	2 drives	80.0%

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.

• 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

Should I optimize this 10-drive plan for capacity 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.

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.

Why include a 10% reserve when planning NAS available space?

Keeping free space improves filesystem behavior for snapshots, metadata, and write performance. Full arrays often perform worse and rebuild more slowly.

How much effective storage does 10x 20TB RAID-Z2 provide?

For QNAP users, this NAS planning scenario estimates 144.00 TB usable after a 10% reserve from 200.00 TB raw.