1. An arrangement for update of cache data in a storage system, the arrangement comprising: memory means for holding data; cache means for holding data associated with the memory means; means for preparing change data for updating the cache means; means for submitting a request for change to the memory means; means for receiving a signal from the memory means representative of completion of the request for change; and means for updating the cache means with the change data in response to the signal indicating successful completion of the request for change.