It goes back again to the value of the data to your organization -- or the impact of losing access to this data.
Typically, from a business continuity perspective, the best way to establish this is through what we call a "business impact analysis," which really measures the impact of an outage on your revenue stream or your organization from a public perception point of view. You need to start from the business processes and look at what applications these business processes depend on -- and then you move down the chain. Once you've identified the application and the dependency, you can start looking at the data that these applications use, and categorize the data based on the business processes that use that data and the importance of those business processes to the organization from a revenue perspective.
Go to the beginning of the Disaster Recovery FAQ Guide