Abstract: A disaster tolerant computer system for protection of electronic databases is achieved by cascading storage controllers to accomplish local and remote disk shadowing. A host computer is connected to a local superordinate storage controller via a local data bus. The superordinate storage controller transmits data via a long haul data link to a remote subordinate storage controller. Additionally, the superordinate controller transmits data to a local subordinate storage controller via a local data bus. Consequently, in-band storage capacity is provided remotely, as well as locally, to increase data storage capacity for database shadowing. Furthermore, the cascading of controllers may be used to increase the effective storage capacity of the computer system by using the increased storage capacity for the writing of non-redundant data.