With the multiple overwrite feature, rewritable optical discs have found application in consumer DVD+RW video recorders, professional archiving systems and computer drives for data storage, replacing the floppy disc in the latter case. Optical Data Storage provides an overview of the recording principles, materials aspects, and application areas of phase-change optical storage. Some theoretical background is given to familiarize the reader with the basics of the phase-change processes. Elements of data recording, including mark formation, eraseability, direct overwrite strategies, data quality and data stability, etc. are explained and extensively discussed. A mark formation model is described and used throughout the whole book to back up measurement results and support the applications discussed. Two major aspects high-speed and dual-layer recording are considered in depth and solutions to achieve higher performance are analyzed.