Building the case for investing in disaster recovery/business continuity begins with defining what functions are critical to your business and tying that to the key systems that support those functions.
Once you've identified those systems, you need to analyze your hardware and software configurations to understand their interdependence and find possible failure points. Next, track your outages, identify their causes, and correlate them to possible points of failure that you've identified.
Then determine the frequency and duration of these outages and identify which points of failure cost your business the most. You need to assign costs to these points of failure and manage these costs to maximize the ROI and minimize the losses felt by the entire organization.
Finally, disaster preparedness and recovery planning are iterative processes -- not a discrete, one-time event. Enterprises should take care to continually revisit their disaster-recovery plans to ensure they remain aligned with current business realities and goals and to test those plans regularly to ensure that they perform as planned.