Toshiba Corp. said Wednesday it has developed a 30-gigabyte dual-layer HD DVD recordable disc, doubling the storage capacity of the single-layer HD DVD-R disc it developed earlier. The Tokyo-based electronics maker plans to roll out next spring an HD DVD recorder compatible with the new disc, it said in a release.The new disc was approved at the Sept. 14 meeting of the DVD Forum's Steering Committee and its technical specifications will be made available, Toshiba said. A DVD-R disc can record data once only. Toshiba is promoting the "HD DVD" as the high-definition successor to the current generation of DVDs, while another group led by Sony Corp. (6758.TO) is promoting a separate format called "Blu-ray Disc."