Comment by wkat4242
Oh ok, I've never done this, but I thought it was already there. Maybe this was the original ZFS from Sun? But maybe I just remember it incorrectly, sorry.
I've used it on multi-drive arrays but I never had the need for expansion.
You could add top level raidz vdevs or replace the members of a raid-z vdev with larger disks to increase storage space back then. You still have those options now.