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10x 6TB RAID-Z2 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 10x 6TB in RAID-Z2. Includes reserve planning for NAS and homelab arrays.

Capacity Snapshot

Raw Capacity

60.00 TB

Usable Capacity

43.20 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	48.60 TB	1 drive	90.0%
RAID 6	43.20 TB	2 drives	80.0%
RAID 10	27.00 TB	1 drive per mirror pair*	50.0%
RAID-Z1	48.60 TB	1 drive	90.0%
RAID-Z2	43.20 TB	2 drives	80.0%

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.

Is RAID-Z2 still viable with 6TB 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 real-world usable storage does 10x 6TB RAID-Z2 provide?

This NAS planning scenario estimates 43.20 TB usable after a 10% reserve from 60.00 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.