We also have Portal running in a active / passive setup. The key for us was making sure we removed all instances of "machine name" from the Portal config. Our setup is also federated, which required a deep tweak (FQN rewrite) within Portal to make it happen. We use RoboCopy to copy deltas from active / passive nightly.
As for Server, we haven't had any luck in getting it to work on our passive side yet. We have ESRI Professional Services looking into a sustainable solution for this.
Just a word of caution that we've found that in order to be 100% reliable we have to shut down the Portal service (and hence postgres) before we copy the Portal database folder to our cold site. If we don't do this we sometimes end up with invalid check points and Postgres fails to start up. I say "sometimes" as we have been successful in most cases with Portal still running but every other start up will fail on the DR site unless Portal is shut down.
The error messages we see in the Event viewer (when we dont shut down Portal) are;
Abhishek
At 10.2.x this isn't really possible OOTB. You need Esri professional services help to implement and to get some custom build libraries for Portal (the OOTB libraries dont support it).
At 10.3 there are instructions to do this yourself.
Trevor
I have been using portalpy to sync content from our DEV/TEST to PROD and DR.