Digital Data Storage (DDS) was introduced in 1989, and used a version of Digital Audio Tape (DAT) for storing data.
DDS used helical scanning on magnetic tape, and stored between 1.3 GB in the first generation (DDS-1) and 36 GB uncompressed on the fifth generation (DAT 72) launched in 2003.
Generally, DDS drives can read and write to media of one or perhaps two previous generations only, so DDS-4 drives cannot read or write from DDS-1 tapes. DDS drives cannot read or write to media from later generations.
Two later generations (DDS-160 and DDS-320) both use 8mm wide tape in a slightly thicker cartridge, whereas the first five generation of DDS used 3.81 mm tape (often labelled as 4mm DDS).
Sources / Resources
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Preservation / Migration
The earliest tapes are now nearly 30 years old