Digital Linear Tape (DLT) originally called CompacTape was developed by Digital Equipment Corporation (DEC) from 1984. In 1994 Quantum Corporation purchased the technology, manufacturing drives. Quantum also licenses the technology and trademark.
A higher capacity variant called Super DLT (SDLT) was developed in 1998. Under license from Quantum a budget line was developed by Benchmark in 1999 and later purchased by Quantum in 2002. All tapes cartridges use linear tape recording in a format known as serpentine, although in reality an outward spiral is used. In 2007 Quantum brought the DLT range of tapes cartridges to an end, shifting their tape data storage strategy to LTO Ultrium tape drives and cartridges.
CompacTape and DLT Cartridges
The original CompacTape data cartridges developed by DEC for the TK range of drives had a rough surface, which if placed into a later drive can damage the read/write heads. With the introduction of DLT III media became a practical tape backup solution, mostly used in mainframe and server environments. The DLT2000 drive allowed up to 10GB of uncompressed data to be recorded onto a single cartridge in 1993. After Quantum bought the technology they introduced the DLT2000XT drive and DLT IIIXT media allowing 15GB of uncompressed data to be stored.
The DLT IV data cartridge was introduced in 1994 with the DLT4000 drive, allowing 20GB of uncompressed data to be recorded. 1996 saw the introduction of the DLT7000 drive which allows 35GB to be stored on a DLT IV data cartridge. The DLT8000 drive extended the DLT IV cartridge capacity to 40GB of uncompressed data. The DLT IV data cartridge was also used in the first two budget drives manufactured by Benchmark, also allowing 40GB of uncompressed data to be stored, at a lower data transfer rate, using proprietary format incompatible with the Quantum recording format. The budget line was extended after the Quantum purchase, allowing 80GB and 160GB on using VS1 media using the DLT-VS160 and DLT-V4 drives respectively.
Super DLT (SDLT)
To extend the storage capacity available, the Super DLT range was created, initially extended the uncompressed capacity to 110GB in 1998, using SDLT 1 media in a SDLT 220 drive, and 160GB in the SDLT 320 drive. The SDLT 600 drive was introduced in 2004, which is able to record 300GB of uncompressed data on SDLT 2 media. The final iteration of the recording format was the DLT-S4 drive manufactured in 2006, is able to store 800GB of uncompressed data onto S4 data cartridges.
DLT Data Recovery and Conversion
Since Quantum brought an end to DLT technology in 2007, the requirement for DLT data recovery has diminished considerably. In spite of this, we still have the knowledge and expertise required to undertake data recovery from any DLT data cartridge.
It is now a legacy media, from which data conversion and electronic disclosure are now the biggest requirement. At DiskEng we have the expertise and experience to recover and convert the data or perform electronic disclosure, whatever the media and backup software used.