Patent ID: 8909862

Claim:
An apparatus comprising: a first device coupled to a first memory, wherein the first memory stores data from a second memory, coupled to a second device, in response to a plurality of write operations issued by the second device; the first device having a cache to store data corresponding to the plurality of write operations prior to writing the data corresponding to the plurality of write operations to the first memory; and a register to store a state of the cache in response to receipt of a special transaction, wherein the first device transmits an acknowledgement to the second device in response to an indication based on content of the register that one or more of the plurality of write operations, which were issued prior to receipt of the special transaction, have been written to the first memory and wherein any write operations occurring after the special transaction are ignored for tracking purposes until an acknowledgement is sent for any pending special transactions, wherein the special transaction causes an acknowledgment to be returned once all previous write operations issued prior to the special transaction have been committed to one of the first memory or the second memory, wherein the apparatus further comprises one or more uninterruptible power sources or batteries to supply power to the one of the first memory or the second memory such that data stored therein is protected even after a power failure.