EU 10x 20TB RAID-Z2 NAS Calculator

Estimate usable TB, parity, and fault tolerance for EU homelab buyers using 10x 20TB in RAID-Z2.

Capacity Snapshot

Raw Capacity

200.00 TB

Usable Capacity

144.00 TB

Fault Tolerance

2 drives

Efficiency

80.0%

Popular TrueNAS default for medium arrays; dual-parity with good safety margin. This scenario applies a 10% filesystem reserve.

Mode	Usable	Tolerance	Efficiency
RAID 5	162.00 TB	1 drive	90.0%
RAID 6	144.00 TB	2 drives	80.0%
RAID 10	90.00 TB	1 drive per mirror pair*	50.0%
RAID-Z1	162.00 TB	1 drive	90.0%
RAID-Z2	144.00 TB	2 drives	80.0%

EU deployments often place additional emphasis on energy efficiency and predictable lifecycle upgrades, especially for always-on NAS fleets.

• Choose a layout that minimizes emergency rebuild risk under continuous operation.
• Prefer capacity plans that survive one upgrade cycle without pool redesign.

Capacity and reliability strategy across multiple hardware refresh cycles.

Intentional free-space margin to protect performance and snapshot behavior.

No. Use this page for pre-purchase sizing, then validate with workload benchmarks, SMART health policy, and a tested restore plan.

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

For long-lived NAS pools, resiliency first is usually safer. Capacity can be expanded later, while a risky parity choice can force migration sooner.

For EU homelab buyers, this NAS planning scenario estimates 144.00 TB usable after a 10% reserve from 200.00 TB raw.