RAIDZ Extension Calculator

RAIDZ extension allows TrueNAS users to add disks one at a time to an existing RAIDZ VDEV, incrementally expanding capacity. Use this calculator to estimate the storage capacity efficiency of a ZFS RAIDZ VDEV after incremental extension.

Existing data blocks retain their original data-to-parity ratio and block width, but are spread across the larger set of disks. New data blocks adopt the new data-to-parity ratio and width, or overhead. Because of this overhead, an extended RAIDZ VDEV can report a lower total capacity than a newly created VDEV with the same number of disks.