ZFS Storage Calculator

Number of Disks

Disk Size (GB)

Redundancy Level

Results

Usable Capacity (Pre-Overhead):

Capacity after redundancy, before ZFS overhead.

Effective Capacity (Actual):

Actual data storage space after redundancy and ZFS overhead.

Calculated ZFS Overhead:

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

Mirror Pairs:

Fault Tolerance:

Redundancy Levels

None (striped): Data is striped across all disks with no redundancy.
Single Parity (raidz1): Data is striped across disks with single parity for fault tolerance.
Double Parity (raidz2): Data is striped across disks with double parity for fault tolerance.
Triple Parity (raidz3): Data is striped across disks with triple parity for maximum fault tolerance.
Mirror Pairs: Data is mirrored across pairs of disks for redundancy.

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. This overhead includes space reserved for metadata, checksums, ZIL (ZFS Intent Log), slop space (to prevent fragmentation issues at high capacity), and partitioning/alignment. This calculator estimates the overhead to provide a more realistic figure than simply subtracting parity disks.