ZFS is probably one of your better options if you want portability. It works on most Unix like operating systems, and due to its zfs send/recv capability you can send your data all over the place - and can trust that it will actually end up the same on the other end. If that's not portability I don't know what is.

If what you're saying is it's not portable to Windows then sure, but compared to most filesystems it's extremely portable.