At present, Bitbucket Server doesn't provide native disaster recovery or high availability functionality. That being said, this is something we plan to address in the future. In the meantime, if you would like to get a feel for the types of home grown failover configurations that our customers have implemented, then I highly recommend posting to our forums over at Atlassian Answers. Answers is a great way to interact with other Bitbucket Server customers, developers, and Atlassian Experts. 

If you would like to monitor our progress on high availability/failover, then I suggest voting and setting a 'watch' on the public feature request here: BSERV-3238: High availability/failover.