Patent ID: 6912669

Claim:
A method for maintaining cache coherency in a system having a first controller and a second controller, comprising: selecting a mirror cache line in a second controller to copy data into; mirroring the data from a cache line in a first controller to the mirror cache line in the second controller; sending a message from the first controller to the second controller informing the second controller of cache meta data associated with data in the mirror cache line; sending a message from the first controller to the second controller requesting ownership of a cache line owned by the second controller; managing a free list of mirror locations in the second controller's cache by the first controller, and managing a free list of mirror locations in the first controller's cache by the second controller, wherein the first and second controllers can copy data into the second and first controller's mirror locations, respectively, and granting ownership of a cache line owned by the second controller, to the first controller, wherein, subsequent to the first controller receiving data that is to be mirrored to the second controller cache line, transferring data to the second controller's cache line from the first controller.