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6x 8TB RAID-Z2 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 6x 8TB in RAID-Z2. Includes reserve planning for NAS and homelab arrays.

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%

NAS Cluster Guides

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

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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: 6x 8TB RAID-Z1 NAS Calculator | Usable TB Next: 6x 10TB RAID 1 NAS Calculator | Usable TB →

FAQ

Why include a 10% reserve when planning NAS storage headroom?

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

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.

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?

This NAS planning scenario estimates 28.80 TB usable after a 10% reserve from 48.00 TB raw.