NAS pSEO Landing

4x 18TB RAID 1 NAS Calculator | Usable TB

Estimate usable TB, parity overhead, and fault tolerance for 4x 18TB in RAID 1. Includes reserve planning for NAS and homelab arrays.

Capacity Snapshot

Raw Capacity

72.00 TB

Usable Capacity

16.20 TB

Fault Tolerance

3 drives*

Efficiency

25.0%

Strong redundancy but low capacity efficiency. Great for small, critical datasets. This scenario applies a 10% filesystem reserve.

Run Interactive Calculator →

Alternative Mode Comparison

Mode	Usable	Tolerance	Efficiency
RAID 5	48.60 TB	1 drive	75.0%
RAID 6	32.40 TB	2 drives	50.0%
RAID 10	32.40 TB	1 drive per mirror pair*	50.0%
RAID-Z1	48.60 TB	1 drive	75.0%
RAID-Z2	32.40 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 16TB RAID-Z2 NAS Calculator | Usable TB Next: 4x 18TB RAID 5 NAS Calculator | Usable TB →

FAQ

How much real-world usable storage does 4x 18TB RAID 1 provide?

This NAS planning scenario estimates 16.20 TB usable after a 10% reserve from 72.00 TB raw.

Is RAID 1 still worth deploying with 18TB drives?

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

How many disk failures can RAID 1 tolerate in this setup?

This setup can tolerate 3 drives*. Real-world survivability depends on mirror placement, rebuild stress, and drive health.

Why include a 10% reserve when planning NAS available space?

Keeping free space improves filesystem behavior for snapshots, metadata, and write performance. Full arrays often perform worse and rebuild more slowly.