There are a lot of tools that can help with disaster recovery, but an effective recovery process circles back to having a well-defined plan of what to do in every scenario. Two things, at least, need to be clearly identified:
What signals a disaster? Some things are obvious (a massive power outage, network loss, or fire), but other situations need to be defined. For example, what signals that a backup server needs to be brought online?
Who responds to a disaster and how? Once a disaster situation occurs, who has the responsibility to act? How are they notified of the event? What are they expected to do?
After a disaster plan is written for each scenario, then test the plan regularly (at least yearly). As the server configuration changes, be sure to update the plan so it reflects the current infrastructure.