ZFS Storage Calculator

Results

Usable Capacity (Pre-Overhead):
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Capacity after redundancy, before ZFS overhead. Displayed in TB.

Effective Capacity (Actual):
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Actual data storage space after redundancy and ZFS overhead. Displayed in TB.

Calculated ZFS Overhead:
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Estimated percentage of total raw capacity used by ZFS metadata, slop space, etc.

Mirror Pairs:
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Fault Tolerance:

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Redundancy Levels Explained

Redundancy levels determine how your data is protected against disk failures. Each level offers a different balance of usable capacity and fault tolerance.

  • None (striped): Data is striped across all disks with no redundancy. If any disk fails, all data is lost.
  • Single Parity (RAIDZ1): Data is striped across disks with single parity for fault tolerance. Can survive the failure of 1 disk.
  • Double Parity (RAIDZ2): Data is striped across disks with double parity for fault tolerance. Can survive the failure of up to 2 disks.
  • Triple Parity (RAIDZ3): Data is striped across disks with triple parity for maximum fault tolerance. Can survive the failure of up to 3 disks.
  • Mirror Pairs: Data is mirrored across pairs of disks for redundancy. Can survive the failure of 1 disk in each mirror pair.

What is Effective Capacity?

Effective capacity represents the actual disk space available for storing your data after accounting for both the chosen redundancy level (like RAIDZ parity or mirroring) and ZFS's internal overhead.

  • Redundancy Level: Space reserved for parity or mirroring to ensure data protection.
  • ZFS Overhead: Includes metadata, checksums, ZIL (ZFS Intent Log), slop space, and partitioning/alignment.

This calculator estimates the overhead to provide a more realistic figure than simply subtracting parity disks. Results are typically shown in Terabytes (TB).