raidz-expansion · shipping · also RAID-Z expansion

RAIDZ expansion

RAIDZ expansion widens an existing RAIDZ virtual device by attaching another member and redistributing allocated space while retaining old blocks' data-to-parity ratios.

OpenZFS 2.3 documents unchanged parity level and different ratios for pre-expansion and newly allocated blocks. [1] This is capacity expansion, not replacement-device resilvering. The implementation records logical widths over transaction-group history to interpret blocks after reflow. [2] See the companion analysis for a bounded accounting model, not a pool-capacity estimator.

Relations

related

raidz, resilver, snapshot, data-scrubbing

Limitations

• The active raidz_expansion feature is not read-only compatible; recovery/import software must support it. [3]

Citations

1. OpenZFS 2.3: zpool-attach(8), RAID-Z expansion and space reporting (accessed 2026-10-16)
2. OpenZFS zfs-2.3.0: vdev_raidz.c, reflow and time-dependent geometry (accessed 2026-10-16)
3. OpenZFS 2.3: zpool-features(7), raidz_expansion compatibility (accessed 2026-10-16)
4. Hesela: RAIDZ expansion and retained parity cost (accessed 2026-10-16)

JSON: /data/terms/raidz-expansion.json