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6x 16TB RAID-Z2 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 6x 16TB in RAID-Z2. Includes reserve planning for NAS and homelab arrays.

Capacity Snapshot

Raw Capacity

96.00 TB

Usable Capacity

57.60 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	72.00 TB	1 drive	83.3%
RAID 6	57.60 TB	2 drives	66.7%
RAID 10	43.20 TB	1 drive per mirror pair*	50.0%
RAID-Z1	72.00 TB	1 drive	83.3%
RAID-Z2	57.60 TB	2 drives	66.7%

NAS Cluster Guides

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

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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.

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.

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 6x 16TB RAID-Z2 provide?

This NAS planning scenario estimates 57.60 TB usable after a 10% reserve from 96.00 TB raw.