A storage system handling storage devices on a floor area while occupying minimal floorspace, comprising a set of transportation assemblies, each adapted for conveying one or more storage devices, and arranged together in a two-dimensional compact puzzle-based configuration. Each transportation assembly comprises a transportation body, at least four autonomous rolling devices connected to the transportation body, each rolling device comprises driving means, communication means, and sensors for autonomous operation when controlled by a central controller unit comprised in the storage system, where the central control unit comprises a computer program product for arranging and re-arranging the set of transportation assemblies in the two-dimensional compact puzzle-based configuration according to position information of each transportation body stored in a database connected to the central control unit and control commands transmitted to the rolling devices.