Zfs Calculator
Calculate ZFS pool capacity, redundancy, and usable space based on drives, RAID level, and failure tolerance.
Published by:
isCalculator Editorial Team
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How to use this tool?
This ZFS Calculator helps you estimate storage capacity and redundancy for various RAID configurations. Follow these steps:
- Enter Number of Drives – Specify the total number of physical drives (minimum 1).
- Enter Drive Size (GB) – Provide the capacity of each drive in gigabytes (e.g., 1000 for 1 TB).
- Select RAID Level – Choose from RAID 0, 1, 5, 6, or 10. Each level has specific drive requirements (e.g., RAID 5 needs at least 3 drives).
- Set Parity Groups / Mirrors – For RAID 1 and RAID 10, specify the number of mirror groups. For RAID-Z (5/6), this is the number of vdevs (usually 1).
- Adjust Overhead (%) – Optionally account for filesystem overhead (e.g., ZFS metadata). Enter 0 if none.
- Click "Calculate" – View results: raw capacity, usable capacity (after parity and overhead), and failure tolerance.
Note: All sizes are in GB (metric). The calculator auto-validates inputs and shows error messages for invalid configurations (e.g., odd drives for RAID 10). The failure tolerance field updates automatically based on your selections.
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Frequently Asked Questions
ZFS is a combined file system and logical volume manager designed by Sun Microsystems, known for data integrity, snapshots, and flexible RAID configurations.
For RAID 5 (single parity), usable capacity = (number of drives - 1) × drive size. One drive's worth of space is used for parity.
Overhead accounts for filesystem metadata, snapshots, or other space reservations. It reduces the usable capacity by that percentage.
