It's also wrong on the opposite front: ZFS cannot change geometries on the fly. I am a fairly big fan of ZFS, but the ability to mix disk sizes and change numbe

It's also wrong on the opposite front: ZFS cannot change geometries on the fly. I am a fairly big fan of ZFS, but the ability to mix disk sizes and change numbers of disks in a RAIDZ set is not why--it effectively cannot do either.