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10x 12TB RAID 5 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 10x 12TB in RAID 5. Includes reserve planning for NAS and homelab arrays.

Capacity Snapshot

Raw Capacity

120.00 TB

Usable Capacity

97.20 TB

Fault Tolerance

1 drive

Efficiency

90.0%

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	97.20 TB	1 drive	90.0%
RAID 6	86.40 TB	2 drives	80.0%
RAID 10	54.00 TB	1 drive per mirror pair*	50.0%
RAID-Z1	97.20 TB	1 drive	90.0%
RAID-Z2	86.40 TB	2 drives	80.0%

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

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FAQ

How much real-world usable storage does 10x 12TB RAID 5 provide?

This NAS planning scenario estimates 97.20 TB usable after a 10% reserve from 120.00 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.

Is RAID 5 still viable with 12TB drives?

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

How many disk failures can RAID 5 tolerate in this setup?

This setup can tolerate 1 drive. Real-world survivability depends on mirror placement, rebuild stress, and drive health.