Patent ID: 6996741

Claim:
A storage area network comprising: a plurality of loosely-coupled storage controllers arranged in a redundant configuration to include only one master storage controller and one or more slave storage controllers, said storage controllers configured to collectively provide virtual storage space to a plurality of servers; a first channel coupled to each of the redundant controllers configured to provide a first path for communication among the storage controllers; a second channel coupled to each of the redundant controllers configured to provide a second path for communication among the storage controllers; a third channel coupled to each of the redundant controllers configured to provide a third path for communication among the storage controllers; and a plurality of physical disk drives coupled to respective back-ends of the storage controllers; wherein the third channel comprises a portion of one or more of the physical disk drives that is accessible to all the storage controllers; wherein each of the portions on the one or more physical disk drives include a first region which is writable only by the master storage controller and a second region which is writable by the slave storage controllers; wherein the second region further comprises: a respective area for each of the slave storage controllers, each said area including: a first section that the master storage controller can write data to and the respective slave storage controller can read data from; and a second section that the respective slave storage controller can write data to and the master storage controller can read data from.