digital data storage (DDS)
Digital Data Storage(DDS) is a further development of Digital Audio Tape( DAT) for professional use in data storage. The recording method used is the helical-scan method, which is also used in video recorders. In the versions DDS-1 to DDS-5, DDS uses a 4 mm tape, like DAT drives; in the version DDS-6, the magnetic tape is 8 mm wide. However, the magnetic tape has improved interference characteristics and is subject to ANSI standards. DDS is characterized by a much lower bit error rate( BER).
The continuous development of DDS has resulted in several DDS generations, which cannot always be played on older DDS drives. The individual DDS versions (DDS-1 to DDS-5) differ in terms of tape length and thus storage capacity as well as data transfer rate.
DDS-1 has a storage capacity of 1.2 GB at a tape length of 60 m, and 2 GB at a tape length of 90 m. The data transfer rates are between 183 KB/s and 366 KB/s.
DDS-2 has a tape length of 120 m and 4 GB storage capacity. Data transfer rates are between 350 KB/s and 750 KB/s.
DDS-3 can store 12 GB of uncompressed data and up to 24 GB of compressed data. Tape length is 125 m, data transfer rate is between 1 MB/s and 1.5 MB/s. Error correction methods are used in DDS-2 and DDS-3, and the read-after-write function is used for data verification, a kind of verify function. The corresponding DAT drive is DAT-24
DDS-4 has a storage capacity of 20 GB uncompressed and 40 GB for compressed data. The tape length is 150 m, and the data transfer rate is 1 MB/s to 3 MB/s.
DDS-5 has a storage capacity of 72 GB for compressed data and a data transfer rate of 3 MB/s. The corresponding DAT drive is DAT-72.
DDS-6 is the 6th generation with a storage capacity of 80 GB/160 GB of compressed data. In addition to the higher storage capacity and a higher data transfer rate, DDS-6 drives can write and read in both directions. The DDS-7 version is the highest expansion level. It has a storage capacity of 160 GB.