Patent ID: 7895287
Filing Date: 2011-02-22
Classification: G06F,H04L

Abstract:
1. A data storage system comprising: a first system including a first network interface to communicate with a host computer, a first storage controller, a first cache table, and a first memory to store a first control program to process an input/output (I/ a second system including a second network interface to communicate with the host computer, a second storage controller, a second cache table, and a second memory to store a second control program to process an I/ an external storage system coupled to the first and second systems, the external storage system including a first storage unit to provide storage volumes and a third storage controller to control the first storage unit, wherein the first and second systems are configured to present the storage volumes of the external storage system to the host computer, wherein each of the first and second cache tables includes state information for each cache entry indicating state of cached data, and wherein said state information of said cache table is informed to said second cache table wherein each of the first and second cache tables further includes address information, and cached data, wherein the state information indicates whether or not a given cached data is CLEAN or DIRTY, wherein CLEAN indicates that the cached data and data stored in a storage volume corresponding to the address information are the same, and wherein DIRTY indicates that the cached data and the data stored in the storage volume corresponding to the address information are different.