Raid rebuild using most vulnerable data redundancy scheme first

A method of managing data in a hierarchical data storage system employing data redundancy schemes includes prioritizing a data rebuild based on a most vulnerable data redundancy scheme in the storage system. A data storage system embodying this rebuild prioritization method is also described. Prioritizing the data rebuild includes enabling a rebuild of the most vulnerable data redundancy scheme prior to enabling a rebuild of any other data redundancy scheme in the system. The most vulnerable data redundancy scheme is determined by comparing a probability of losing data that can be prevented by a rebuild for each data redundancy scheme with respect to the potential for one or more next storage device failures in the data storage system. The probability of losing data for each data redundancy scheme is determined by considering characteristics associated with the storage system and disk drives in the storage system, including number of storage devices, mean time between failure, mean time or calculated time to rebuild, and failure dependencies.