High-Definition DVD is a new format of optical storage that is primarily intended to store High Definition video data. It was also called Advanced Optical Disk. It is incompatible with Blu-ray disc technology. It uses a blue violet laser with wavelength of 405 nanometres. It is capable of storing 15 gigabytes of data on a single layer and 30 GB in dual-layer. HD-DVD disks appear in the following types: HD-DVD RAM (read and write), HD-DVD ROM (readonly; all pre-manufactured discs), HD-DVD—R (read once), and HDDVD— RW (read and write ). The data transfer rate of the first HDDVD drive was 4.36 Megabytes per second.