Abstract: Modular data storage and retrieval system having data cells for holding a plurality of optical storage cartridges, drive cells for holding devices such as drives for transcribing data on the cartridges, and a back plate on which the cells can be mounted in any desired combination. Two types of mounting positions are provided, one for either data cells or drive cells, the other for data cells. Two or more sections of the system can be placed side-by-side, stacked and/or placed back-to-back to provide a larger system. Each section is provided with at least one picker for moving the cartridges between the cells in the section. In some embodiments, a single picker is provided for each section, and in other embodiments a separate picker is provided for each row of cells. The back plates have registration pins which engage sockets on the cells to assure accurate alignment of the cells on the plates. The cells are symmetrical with regard to the way they mount, and they can be oriented in two different positions, e.