Not the entire boot volume, but close. People have put user directories, etc. on ZFS drives. Google "MacZFS" for an older version (ZFS v8) or "Zevo Community Ed

Not the entire boot volume, but close. People have put user directories, etc. on ZFS drives. Google "MacZFS" for an older version (ZFS v8) or "Zevo Community Edition" for a more modern version (ZFS v28). There're active discussion boards for both.