Question: If I have two identical servers running with different IP addresses, can PeerSync change the IP in my remote DNS to point to the other data center that's still up if a data center goes down?
Answer: PeerSync is designed to synchronize/backup the data from one server to another. In your case, PeerSync could be used to keep a real-time backup of all the files and data from the primary server onto the backup server, which your users could then reference after the IP address was changed in the DNS.
Any changes or modifications which may need to be made to the data in order to function on the backup server (such as importing the data into an application, updating any machine-specific configuration files, etc.) will need to be performed manually, as PeerSync will make sure the data folders are mirrored however it does not provide automatic failover.