Digital Linear Tape
The Digital Linear Tape (DLT) is in Information Technology, a formerly developed by Digital Equipment Corporation, now Quantum magnetic storage medium for data protection (backup ) and archiving of digital data.
In the DEC MicroVAX II, the very well-known experts in DEC TK50 drive was included as standard from about 1984 for the first time, which was II forerunner of today's DLT technique with his successor TK70 and the media CompacTape I or CompacTape.
With DLT media data can be transferred faster than with other technologies in this area such as QIC; currently has the current variant S- DLT to the three most efficient tape technology.
The devices include a switchable hardware compression with the secured data can be compressed. The manufacturers are usually made from a 2:1 compression - ie reduction by half. This information is highly dependent on the data being backed up, and in practice is often not realistic. Therefore, in this article, only the uncompressed capacity is specified.
In the mid-range segment DLT libraries and robotic solutions are automated archiving large amounts of data available.
Technology
At DLT media tracks run parallel to the edge of the tape to write and read the tape is guided accurately by pulled in multiple directions to the moving write head serpentine; this process is called linear recording (see: helical scanning with DAT media).
Technical features of DLT are:
- Oblique azimuth of the magnetic gaps at DLT 7000 and DLT 8000 depending on the direction for optimum utilization of bandwidth by avoiding (magnetic ) track intervals
- Parallel recording of 4 tracks simultaneously
- S- DLT: progression to higher capacities with higher track density by laser scanning with a rear optical servo track.
On the front of the cartridge, with a slider to lock the media from being overwritten. For example, if the viewing window, a red mark ( there are also other types of displays ), the belt is locked for writing.
The drives indicate problems caused by pollution write by a LED on the device. In this case, a special cleaning tape (cleaning cartridge) must be inserted, which cleans the drive head. The cleaning tapes are usually provided for 20 applications.
Variants
Media
Depending on drive used, the capacity may vary ( a DLT 8000 drive can write, for example, 40 GB on a DLT tape IV, on the other hand a DLT 7000 drive is only 35 GB, and a DLT 4000 drive is only 20 GB ). Drives for DLT III and DLT IV media are mutually largely backward compatible. SDLT drives can read DLT-IV media only and do not describe. DLT III- media can not be read with SDLT drives.
DLT media
DLT media contains a 1/2 inch ( 12.6 millimeter ) wide magnetic tape in a cartridge (cassette) is encapsulated. The use of the DLT and SDLT logos ( trademarks ) was purchased from Quantum licensed only to the companies (paid) that meet the strict quality requirements. The actual media manufacturers are Fujifilm, Hitachi / Maxell and Imation (formerly 3M). The patent on the actual ( ATOMM ) magnetic tape holds Fujifilm. DLT media are considered more reliable and more suitable for long-term archiving, because they should only lose about 5 percent of their magnetization in 30 years.
The media manufacturer Imation sued in October 2001, Quantum infringement of competition law since lizenziere Quantum DLT / S- DLT trademark rights ( trademarks ) only to certain companies and for allegedly demanded excessive license fees. The U.S. court dismissed the complaint by Imation and decided that the company had to pay 30 percent of its income from the sale of DLT media as royalties to quantum (see, on the allegations: ,, to the court decision :). Under pressure of the court had been agreed upon and Imation is now ( again ) the third tape and DLT cartridges manufacturers worldwide.