Digital Data Storage ( DDS ) is a computer data storage technology that is based upon the Digital Audio Tape (DAT) format that was developed during the 1980s. DDS is primarily intended for use as off-line storage, especially for generating backup copies of working data.
7-416: A DDS cartridge uses tape with a width of 3.81mm, with the exception of the latest formats, DAT-160 and DAT-320, both which use 8mm wide tape. Initially, the tape was 60 meters (197 feet) or 90 meters (295 ft.) in length. Advancements in materials technology have allowed the length to be increased significantly in successive versions. A DDS tape drive uses helical scan recording, the same process used by
14-517: A video cassette recorder (VCR). Backward compatibility between newer drives and older cartridges is not assured; the compatibility matrices provided by manufacturers will need to be consulted. Typically drives can read and write tapes in the prior generation format, with most (but not all) also able to read and write tapes from two generations prior. Notice in HP's article that newer tape standards do not simply consist of longer tapes; with DDS-2, for example,
21-469: A rotating head drum, which moves the chips at high speed by due to its high angular velocity. The speed of the head chips must be higher than the linear speed of the tape. The tape is wrapped tightly around the drum. The drum and/or the tape is tilted at an angle that allows the head chips to read the tape diagonally. The linear speed of the tape is slower than the speed of the head chips, allowing high frequency signals to be read or recorded, such as video. As
28-446: The length of the tape. The diagonal tracks read or written using this method are known as helical tracks. There are several types of helical scan. These include: Many helical scan cassette formats such as VHS and Betacam use a head drum with heads that use azimuth recording , in which the heads in the head drum have a gap that is tilted at an angle, and opposing heads have their gaps tilted so as to oppose each other. This eliminates
35-518: The need for guard bands between the helical tracks allowing for a higher density of information on the tape. Earl Edgar Masterson from RCA patented the first helical scan method in 1950. German engineer Eduard Schüller developed a helical scan method of recording in 1953 while working at AEG. With the advent of television broadcasting in Japan in the early 1950s, they saw the need for magnetic television signal recording. Dr. Kenichi Sawazaki developed
42-546: The tape moves linearly or length-wise, the head chips move across the width of the tape in a diagonal path. Due to geometry, this allows for high head chip speeds, known as writing speeds, to be achieved in spite of the low linear speed of the tape. The high writing speed allows for high frequency signals to be recorded. As each head chip enters into contact with the tape, it creates or reads long and narrow areas with information recorded magnetically known as tracks. In Helical scan, these tracks are positioned diagonally, relative to
49-729: The track was narrower than with DDS-1. At one time, DDS competed against the Linear Tape-Open (LTO), Advanced Intelligent Tape (AIT), VXA , and Travan formats. However, AIT, Travan and VXA are no longer mainstream, and the capacity of LTO has far exceeded that of the most recent DDS standard, DDS-320. The next format, Gen 8, was canceled. Helical scan Helical scan is a method of recording high-frequency signals on magnetic tape , used in open-reel video tape recorders , video cassette recorders , digital audio tape recorders, and some computer tape drives . With this technique, magnetic tape heads (or head chips) are placed on
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