Method and apparatus for recovering redundant cache data of a failed controller and reestablishing redundancy

Abstract

A method, and apparatus for recovering cache data of a failed redundant storage controller and reestablishing redundancy by mirroring cache data of a primary cache memory of a first storage controller in a secondary cache memory of another storage controller. Upon a failure occurring in a storage controller, the failure is detected and, in response, a structured list of cache tags is created in the controller where having the secondary cache that is the mirror of the primary cache of the failed controller. The primary cache memory of the non-failed storage controller that was mirrored in the secondary cache of the failed controller and the secondary cache memory of the non-failed storage controller that was linked to the primary cache of the failed controller are flushed, and an available secondary cache memory, which may be the secondary cache memory just flushed, is configured to function as a redundant cache memory for the primary cache memory of the non-failed storage controller that was mirrored in the secondary cache of the failed controller, such that cache data in the primary cache memory of the non-failed storage controller is mirrored in the available secondary cache memory.