NAS planning example

2x 8TB RAID 1 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 2x 8TB in RAID 1. Includes reserve planning for NAS and homelab arrays.

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Planning route

Answer the capacity question, then validate the purchase path

Use this worked example as a numeric starting point, then validate the RAID choice, capacity reserve, hardware plan, and backup path.

Decision aid RAID level selector Reference Capacity matrix

Editorial method

What this calculator can—and cannot—decide

The capacity model makes drive count, drive size, RAID layout, and reserve visible. It is a planning aid: it does not predict exact performance, rebuild duration, hardware compatibility, or the probability of data loss for a specific system.

Last reviewed: July 10, 2026. Product links remain neutral category searches until a partner relationship and page-level disclosure are in place.

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Capacity Snapshot

Raw Capacity

16.00 TB

Usable Capacity

7.20 TB

Fault Tolerance

1 drives*

Efficiency

50.0%

Strong redundancy but low capacity efficiency. Great for small, critical datasets. This scenario applies a 10% filesystem reserve.

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Alternative Mode Comparison

Mode	Usable	Tolerance	Efficiency
RAID 5	N/A	N/A	N/A
RAID 6	N/A	N/A	N/A
RAID 10	N/A	N/A	N/A
RAID-Z1	N/A	N/A	N/A
RAID-Z2	N/A	N/A	N/A

NAS cluster navigation

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NAS Hub Calculator and buying path Learning Center 8-step guide path RAID Comparison Mode-by-mode matrix RAID Selector Choose by priority Capacity Matrix Citation-ready reference NAS FAQ Planning answers

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Sequential long-tail navigation

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FAQ

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 1 still practical with 8TB drives?

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

How much effective storage does 2x 8TB RAID 1 provide?

This NAS planning scenario estimates 7.20 TB usable after a 10% reserve from 16.00 TB raw.

How many disk failures can RAID 1 tolerate in this setup?

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