A multiple-drive data-storage system includes a multiple-drive controller, a fixed-media disk drive, and a removable-media, optical-disk disk drive. Preferably, the controller is defined on a printed circuit board assembly attached to a head disk assembly containing the fixed media, and includes a host interface and a command decoder for receiving and decoding commands. A shared buffer memory has allocated storage space for data read from the fixed-media and from the removable optical disks. An error corrector corrects data errors including errors in address-defining data retrieved from headers in the removable optical disks. Caching of data read from the optical disks onto the fixed media allows high speed operation of the combined system and reduced blocking of the host I/O bus.