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3x 6TB RAID 5 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 3x 6TB in RAID 5. Includes reserve planning for NAS and homelab arrays.

Capacity Snapshot

Raw Capacity

18.00 TB

Usable Capacity

10.80 TB

Fault Tolerance

1 drive

Efficiency

66.7%

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 10.80 TB 1 drive 66.7%
RAID 6 N/A N/A N/A
RAID 10 N/A N/A N/A
RAID-Z1 10.80 TB 1 drive 66.7%
RAID-Z2 N/A N/A N/A

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

← Previous: 3x 6TB RAID 1 NAS Calculator | Usable TB Next: 3x 6TB RAID-Z1 NAS Calculator | Usable TB →

FAQ

How much real-world usable storage does 3x 6TB RAID 5 provide?

This NAS planning scenario estimates 10.80 TB usable after a 10% reserve from 18.00 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.

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 3-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.