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Digital Linear Tape. Tape storage developed in the late seventies by Digital Equipment Corporation (otherwise known as DEC), and the basis for successive generations of DLT tape drive which higher storage capacities and transfer rates. Most DLT drives are backwards compatible but this is not guaranteed, so check. DLT tapes use half inch tape media, fully enclosed in a sealed case which is designed only to open when the tape is in the drive.
Type Native capacity 1 Notional capacity 2 Native backup rate 3
DLT 2000 10GB 20GB 1.25Mbps
DLT 4000 20GB 40GB  
DLT 7000 35GB 70GB 5Mbps
DLT 1 40GB 80GB 3Mbps
DLT 8000 40GB 80GB 6Mbps
SDLT 1 110GB 220GB 11Mbps
SDLT 220
SDLT 320 160GB 320GB 16Mbps


  1. Native capacity is with no compression applied.
  2. Notional capacity is with hardware compression applied. Quoted figures normally assume a compression ratio of 2:1 but this will vary with real data.
  3. Drives are often quoted with a "Notional backup rate", which is the rate at which data can be written to the tape with an assumed 2:1 compression ration. The notional backup rate is therefore double the native backup rate.

DLT has generally lost out in favour of LTO.

See also: DDS, SDLT, LTO.

For more information see: