NAS planning example

RAID-Z3 vs RAID-Z2 Calculator

Compare usable TB, parity cost, and fault tolerance between RAID-Z3 and RAID-Z2 for NAS and homelab arrays.

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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Comparison Notes

This page compares RAID-Z3 and RAID-Z2 on identical hardware assumptions to help homelab builders choose between capacity efficiency and fault tolerance.

Disk size baseline: 8TB drives
Reserve policy: 10% filesystem headroom
Use the interactive tool for exact real-world constraints

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Storage Capacity Table

Drives	RAID-Z3	RAID-Z2	Delta
4x 8TB	N/A	14.40 TB	N/A
6x 8TB	21.60 TB	28.80 TB	-7.20 TB
8x 8TB	36.00 TB	43.20 TB	-7.20 TB
10x 8TB	50.40 TB	57.60 TB	-7.20 TB
12x 8TB	64.80 TB	72.00 TB	-7.20 TB

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: RAID 10 vs RAID 6 Calculator | NAS Capacity Next: RAID 0 vs RAID 10 Calculator | NAS Capacity →

FAQ

Which has more real-world usable available space: RAID-Z3 or RAID-Z2?

This NAS planning scenario compares both modes at fixed drive sizes so you can see usable capacity differences before buying disks.

Does this comparison include filesystem reserve?

Yes. The comparison table applies a 10% reserve baseline to reflect realistic operating headroom in NAS and homelab environments.

Can two layouts with similar storage headroom still have very different failure exposure?

Yes. Similar usable TB does not imply similar failure tolerance or rebuild exposure. Capacity and resiliency should be evaluated together.

How should I pick between RAID-Z3 and RAID-Z2?

Choose based on your risk tolerance, rebuild window, and performance profile. Higher parity usually lowers capacity but improves resilience.