Hi,
I understand you have 2 SBG boxes (both are scanner + control center at the moment).
There's not active passive feature at the moment and there's no way to have 2 control centers talking to the same scanner.
Going back to first post, one solution to the logging question can be to use remote logging vis Syslog. You can configure SBG to send all your logs to a host that will collect everything that is generated by each of the SBG appliances when running and you don't need to replicate anything this way (this is for logs).
If you want to have one appliance running and the other as a spare with same configuration, you then need to do backups on SBG 1 and restore it on SBG 2. You can even schedule regular backups on SBG.
Another option is to have both appliances running separately (and maybe still doing scheduled backups).
Hope this helps,
Federico