Abstract: A method and apparatus is disclosed for reliably storing data to be written to a peripheral device subsystem. The method disclosed includes the following steps. A first peripheral device controller, which includes a cache memory, receives write data from a central processor, stores it in its cache memory, and transmits a copy of it to a second peripheral device controller via a communications path. The second controller, which also includes a cache memory, stores the copy of the write data transmitted to it in its cache memory. Meanwhile the first controller processes the write data. In the event the first controller fails, the second controller processes the write data stored in its cache memory. The apparatus disclosed includes a central processor which generates write data. A first peripheral device controller, which includes a cache memory, is coupled to the central processor.