NAS planning example

5x 6TB RAID 6 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 5x 6TB in RAID 6. 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

Turn the result into a storage brief

The capacity model makes drive count, drive size, RAID layout, and reserve visible. Use the resulting brief to check exact performance, rebuild duration, hardware compatibility, and the recovery plan for the chosen system.

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

OpenZFS checksums and scrubs Background on checksum verification, scrubs, and repair in suitably redundant ZFS pools. Read primary source ↗ TrueNAS data protection Official overview of scrubs, S.M.A.R.T. tests, snapshots, replication, and backup tasks. Read primary source ↗ CISA ransomware guidance Why recoverable, regularly tested backups should be separate from array redundancy. Read primary source ↗

Capacity Snapshot

Raw Capacity

30.00 TB

Usable Capacity

16.20 TB

Fault Tolerance

2 drives

Efficiency

60.0%

Safer for larger arrays with dual parity, at the cost of one extra parity disk. This scenario applies a 10% filesystem reserve.

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Alternative Mode Comparison

Mode	Usable	Tolerance	Efficiency
RAID 5	21.60 TB	1 drive	80.0%
RAID 6	16.20 TB	2 drives	60.0%
RAID 10	N/A	N/A	N/A
RAID-Z1	21.60 TB	1 drive	80.0%
RAID-Z2	16.20 TB	2 drives	60.0%

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

← Previous: 5x 6TB RAID 5 NAS Calculator | Usable TB Next: 5x 6TB RAID-Z1 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.

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 5-drive plan for capacity 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 much usable storage does 5x 6TB RAID 6 provide?

This NAS planning scenario estimates 16.20 TB usable after a 10% reserve from 30.00 TB raw.