Or growing by adding a whole additional DAS full of disks, and yes... zfs supports adding vdevs to pools. So if you have a 6disk raidz2, you can append another

Or growing by adding a whole additional DAS full of disks, and yes... zfs supports adding vdevs to pools. So if you have a 6disk raidz2, you can append another 6disk raidz2 to it to "grow" your pool. More commonly though, is probably adding new raid1 pairs to a raid10.