US Patent 8140800 Storage apparatus

Upon receiving an access request from a server, a microprocessor allocates a free slot as a data storage destination that is different from the LU# and LBA designated as a storage destination of user data, stores user data and data identifying information for identifying the user data in the free slot, and zero-clears the pre-updated data slot designated with the LU# and LBA. During a subsequent read access, the microprocessor accesses the data slot and, if the read data identifying information and the data identifying information designated in the read access from the server coincide, transfers this read data to the server as correct data, and, if the read data identifying information and the data identifying information designated in the read access from the server do not coincide, performs processing for recovering correct data based on the read data identifying information.