Patent ID: 8028191

Claim:
A controller device for use as one of a set of caching controller devices connected by a network and sharing access to a redundancy group, comprising: an array management function (AMF) providing access to the redundancy group; and a communications port for coupling to the network, wherein the AMF is a first AMF operative to communicate over the network with the redundancy group and with one or more second AMFs distributed among the caching controller devices and sharing access to the redundancy group, the second AMFs including one or more sharing partners and one or more replication partners, the sharing partners maintaining caches for satisfying read and write requests for data of the redundancy group, the replication partners capable of receiving write data from the first AMF and writing the replicated data to a physical storage device if the controller device fails, at least one of the replication partners also being one of the sharing partners, and wherein the first AMF is further operative, in response to a write request from a host to write data to the redundancy group, to: (a) send an invalidate request to one or more of the sharing partners, the invalidate request indicating that any copies of the data cached at the sharing partners are stale and are to be invalidated; (b) safely store the data by a selected one of (i) in the event that write-through caching is employed, writing the data to a physical storage device, and (ii) in the event that write-back caching is employed, replicating the data to one or more of the replication partners; and (c) return a write acknowledgment to the host only upon safely storing the data.