Hi,
First of all, SolidFire is a purely SAN Machine (iSCSI only) working on SSD drives.
At the moment, latest OS (Element 10) and latest release of ONTAP (9.3) are compatible using snapmirror.
BUT
- LUN replicated from SF to FAS will not be usable by FAS only a resync to SF will be doable for now.
Hope it helped..