← NAS & RAID Calculator

NAS pSEO Landing

3x 18TB RAID-Z1 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 3x 18TB in RAID-Z1. Includes reserve planning for NAS and homelab arrays.

Capacity Snapshot

Raw Capacity

54.00 TB

Usable Capacity

32.40 TB

Fault Tolerance

1 drive

Efficiency

66.7%

ZFS single-parity equivalent of RAID 5; common for smaller homelab pools. This scenario applies a 10% filesystem reserve.

Run Interactive Calculator →

Alternative Mode Comparison

Mode Usable Tolerance Efficiency
RAID 5 32.40 TB 1 drive 66.7%
RAID 6 N/A N/A N/A
RAID 10 N/A N/A N/A
RAID-Z1 32.40 TB 1 drive 66.7%
RAID-Z2 N/A N/A N/A

NAS Cluster Guides

NAS Hub RAID Level Compare RAID Capacity Matrix Planning Quick Sheet RAID Selector NAS FAQ

Related Long-Tail Calculators

2x 4TB RAID 1 2x 6TB RAID 1 2x 8TB RAID 1 2x 10TB RAID 1 2x 12TB RAID 1 2x 14TB RAID 1 2x 16TB RAID 1 2x 18TB RAID 1 2x 20TB RAID 1 3x 4TB RAID 1 3x 4TB RAID 5 3x 4TB RAID-Z1 3x 6TB RAID 1 3x 6TB RAID 5 3x 6TB RAID-Z1 3x 8TB RAID 1

Sequential Long-Tail Navigation

← Previous: 3x 18TB RAID 5 NAS Calculator | Usable TB Next: 3x 20TB RAID 1 NAS Calculator | Usable TB →

FAQ

How many disk failures can RAID-Z1 tolerate in this setup?

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

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 3-drive plan for available space 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.

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.