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Abstract

A fiber channel storage area network (SAN) provides virtualized storage space for a number of servers to a number of virtual disks implemented on various virtual redundant array of inexpensive disks (RAID) devices striped across a plurality of physical disk drives. The SAN includes plural controllers and communication paths to allow for fail-safe and fail-over operation. The plural controllers can be loosely-coupled to provide n-way redundancy and more than one independent channel for communicating with one another. In the event of a failure involving a controller or controller interface, the virtual disks that are accessed via the affected interfaces are re-mapped to another interface in order to continue to provide high data availability. In particular a resource re-allocation routine operating on one of the controllers employs predetermined criteria against a family of potential back-up controllers in order to select appropriate back-up controllers for a particular device that fails. The criteria, for example, can include an explicit primary/secondary table to control selecting a secondary controller for any primary controller or be more complex so as to consider such statistics as data transfer loads among the interfaces, data transfer loads among the controllers, or the number of targets assigned to each interfaces.

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