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Digital Data Storage, also known (incorrectly) as DAT or 4mm tape or drive. cf DLT. Tape capacities vary:
Type Tape length Native capacity 1 Notional capacity 2
DDS-1 DDS-60 60m 1.3GB 2.6GB
DDS-90 90m 2GB 4GB
DDS-2 DAT 8 120m 4GB 8GB
DDS-3 125m 12GB 24GB
DDS-4 150m 20GB 40GB
DDS-5 DAT 72 170m 36GB 72GB


  1. Native capacity is the amount of data that can be stored on the tape with no compression applied.
  2. Notional capacity (which is normally how vendors tend to rate the tapes and drives) assumed hardware compression of 2:1, but this will vary with real data.

For more information see: