QNAP 8x 20TB RAID 5 NAS Calculator

Estimate usable TB, parity, and fault tolerance for QNAP NAS users using 8x 20TB in RAID 5.

Capacity Snapshot

Raw Capacity

160.00 TB

Usable Capacity

126.00 TB

Fault Tolerance

1 drive

Efficiency

87.5%

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	126.00 TB	1 drive	87.5%
RAID 6	108.00 TB	2 drives	75.0%
RAID 10	72.00 TB	1 drive per mirror pair*	50.0%
RAID-Z1	126.00 TB	1 drive	87.5%
RAID-Z2	108.00 TB	2 drives	75.0%

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

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

Sequential Long-Tail Navigation

← Previous: Synology 8x 20TB RAID 5 NAS Calculator Next: TrueNAS 8x 20TB RAID 5 NAS Calculator →

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.

Should I optimize this 8-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.

Is RAID 5 still worth deploying with 20TB drives?

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

How much usable storage does 8x 20TB RAID 5 provide?

For QNAP users, this NAS planning scenario estimates 126.00 TB usable after a 10% reserve from 160.00 TB raw.