calc.engineer / Homelab & Networking / ZFS Capacity

ZFS Capacity v1.0.0

Calculate usable ZFS pool capacity for any RAID level including stripe, mirror, raidz1, raidz2, and raidz3. Computes raw capacity, parity overhead, data disk count, usable terabytes after ZFS metadata overhead (checksums, block pointers, uberblocks), and storage efficiency percentage. Essential for planning NAS builds, TrueNAS/ZFS server storage, and estimating how much usable space a given disk configuration will provide. Supports variable disk sizes and configurable metadata overhead.

feeds zfs_ram →
Total number of physical disks in the pool
Size of each individual disk in terabytes
ZFS RAID level: stripe (no redundancy), mirror (2-way), raidz1/2/3 (single/double/triple parity)
ZFS record size in kilobytes, affects compression and performance
Percentage of raw capacity consumed by ZFS metadata, checksums, and internal structures
Fill in the inputs and Compute to see the structured result.

From an agent (MCP) or the API

curl -X POST https://calc.engineer/api/zfs_capacity \
  -H "Content-Type: application/json" \
  -d '{"disk_count": …, "disk_size_tb": …, "raid_type": …}'

MCP: connect to https://calc.engineer/mcp and call zfs_capacity.

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