The recordable BD includes BD-R, which can be written once, and BD-RE, which can be written and erased many times. A single-layer BD can hold 25 GB data, and a double layer BD can hold 50 GB data. Feasibility studies from various manufacturers demonstrate that when 4, 6, 10, or even 20 multirecoding layer techniques are used, a much greater data capacity, up to 500 GB, can be achieved. Because of the much larger data size each disk can hold, and because the base writing speed is much faster, 3 times faster than that of a DVD, it is anticipated that with the BD disk technology advancement, Blu-ray will replace the regular DVD for PACS/EHR secondary back-up long-term storage. The data writing speed for a recordable CD, DVD, and BD are listed in Table 5.1.