Is it possible to setup 2 Plesk servers with the same data so that one is acted as a backup server? It's called redandancy.
This functionality is not supported in Plesk at the moment. You may want to suggest new functionality in Plesk on Plesk User Voice portal.
The top-ranked suggestions are likely to be included in the next versions of Plesk. You can get the information about the updates in our products in the following public sources:
https://partners.plesk.com/ - public roadmaps for partners;
http://kb.plesk.com/subscriptions/index.html - knowledge base, each product update comes with corresponding KB article;
http://kb.plesk.com/rss/?p=PLESK - RSS feeds