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5x 18TB RAID 5 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 5x 18TB in RAID 5. Includes reserve planning for NAS and homelab arrays.

Capacity Snapshot

Raw Capacity

90.00 TB

Usable Capacity

64.80 TB

Fault Tolerance

1 drive

Efficiency

80.0%

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 64.80 TB 1 drive 80.0%
RAID 6 48.60 TB 2 drives 60.0%
RAID 10 N/A N/A N/A
RAID-Z1 64.80 TB 1 drive 80.0%
RAID-Z2 48.60 TB 2 drives 60.0%

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: 5x 18TB RAID 1 NAS Calculator | Usable TB Next: 5x 18TB RAID 6 NAS Calculator | Usable TB →

FAQ

How much real-world usable storage does 5x 18TB RAID 5 provide?

This NAS planning scenario estimates 64.80 TB usable after a 10% reserve from 90.00 TB raw.

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.

Is RAID 5 still viable with 18TB drives?

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

Should I optimize this 5-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.