BFI does not have an HA feature and it is not planned to have one (like two instances of BFI synchronizing each other).
It is possible though to set up two instances of BFI that will talk to the same Bigfix server. Both shall get the same data because BFI does not change data on Bigfix server side.
Such approach is not documented and therefore not maintained by BFI.
On the side about backup of BFI db. BFI db database can be recreated based on Bigfix db.