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4x 12TB RAID-Z1 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 4x 12TB in RAID-Z1. Includes reserve planning for NAS and homelab arrays.

Capacity Snapshot

Raw Capacity

48.00 TB

Usable Capacity

32.40 TB

Fault Tolerance

1 drive

Efficiency

75.0%

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

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Alternative Mode Comparison

Mode Usable Tolerance Efficiency
RAID 5 32.40 TB 1 drive 75.0%
RAID 6 21.60 TB 2 drives 50.0%
RAID 10 21.60 TB 1 drive per mirror pair* 50.0%
RAID-Z1 32.40 TB 1 drive 75.0%
RAID-Z2 21.60 TB 2 drives 50.0%

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: 4x 12TB RAID 10 NAS Calculator | Usable TB Next: 4x 12TB RAID-Z2 NAS Calculator | Usable TB →

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.

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.

Is RAID-Z1 still worth deploying with 12TB drives?

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

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.