Expanding 1-disc storage is trivial. Scenario 1: Replace smaller disc with bigger disc. Add new disc as mirror to vdev. Wait for it to resilver. Remove orig

Expanding 1-disc storage is trivial. Scenario 1: Replace smaller disc with bigger disc. Add new disc as mirror to vdev. Wait for it to resilver. Remove original disc from vdev. Pool will autoexpand to new disc size or can be manually expanded otherwise. Scenario 2: Expand virtual storage. Use LVM lvresize, or expand VM virtual disc. Pool will autoexpand to new volume size; may need manual triggering if the system doesn't pick up the new device size automatically. Or you can do the same as for physical discs. Add new virtual storage as mirror, resilver, then drop the old storage.