Abstract: A mass memory storage device has a plurality of optical disks that the rotation axes of each disk being mounted equidistantly from a main axis. An arm is rotatably mounted about the main axis and is selectively positioned adjacent one of the addressed disks. A transducer head is carried on the distal end of the arm and is operably positioned adjacent an addressed track on the addressed disk. The arm may have two branches at its distal end where each branch carries a transducer head so that data can be read from and written to each side of the disk. Further, about each rotation axis of a disk, may be disposed a plurality of disk coaxially aligned to increase the storage capacity of the memory device.