We are doing this on one of our customers sites now. What we do is have gateway on each spoke machine with complete project and MSSQL databases on each. So if we loose radio communications then we loose no data. On these spoke machines we run the tag history splitter to push historical data to spoke and hub at the same time. If radio to hub is down then the store and forward system is configured in such a way that we loose no data going to the hub. You will also want to setup a secondary Alarm Journal to push to the hub all of your alarms. You can also do the same thing with any transaction groups and just setup a secondary copy to push data to the hub database.
That’s kind of the basic system but this approach is working good for us here. I’m sure there are lots of other doing this type thing also and I’m sure there are many ways of getting it done this is just how we are handling the basic end of things.