Digital linear tape
| Storage medium Digital Linear Tape (DLT)
|
|
 External DLT-7000 drive with inserted tape (above an external DVD burner for size comparison) |
|
| General | |
|---|---|
| Type | Magnetic tape |
| capacity | up to 800 GB |
| use | data backup |
| origin | |
| developer | Digital Equipment Corporation |
| Launch | 1984 |
The digital linear tape ( DLT ) is in information technology , a formerly of Digital Equipment Corporation , now Quantum developed magnetic storage medium for data backup ( Backup ) and archiving digital data.
In the DEC MicroVAX II, the DEC- TK50 drive, which is very well known to experts, was installed in series for the first time from around 1984. Together with its successor TK70 and the CompacTape I and CompacTape II media, it was the forerunner of today's DLT technology.
With DLT media, data can be transferred faster compared to other technologies in this area such as QIC ; The current S-DLT variant is currently one of the three most efficient belt technologies.
The drives have a switchable hardware compression with which the data to be backed up can be compressed. The manufacturers usually assume a 2: 1 compression - that is, a reduction by half. This specification depends heavily on the data to be backed up and is usually not realistic in practice. Therefore, only uncompressed capacity is given in this article.
In the midrange segment, DLT libraries and robot solutions are available for the automated archiving of large amounts of data.
technology
With DLT media, the tracks run parallel to the edge of the tape, while writing and reading the tape is precisely guided in several directions and pulled past the movable read / write head in a serpentine manner; this process is called linear recording (see also: helical track recording with DAT media).
Technical features of DLT are:
- Inclined azimuth of the magnetic gaps in the DLT-7000 and DLT-8000 depending on the direction of travel for optimal use of the bandwidth by avoiding (magnet) track gaps
- Parallel recording of 4 tracks at the same time
- S-DLT: Further development to higher capacities with higher track density through laser scanning with an optical servo track on the back.
There is a slider on the front of the cartridge to prevent the media from being overwritten. If z. B. The viewing window shows a red mark (there are also other types of display), the tape is blocked for writing.
The drives indicate problems caused by a dirty read / write head with an 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 intended for 20 uses.
variants
| default | Capacity [GB] | interface | Data rate [MB / s] | date | medium | ||
|---|---|---|---|---|---|---|---|
| native | compressed | native | compressed | ||||
| TK50 / TZ30 | 0.095 | proprietary / SCSI | 0.045 | 1984 | CT I. | ||
| TK70 | 0.295 | proprietary | 0.045 | 1987 | CT II | ||
| THZ01 / DLT260 / Tx85 | 2.6 | DSSI / SCSI | 0.8 | 1989 | DLT III | ||
| THZ02 / DLT600 / Tx86 | 6th | DSSI / SCSI | 0.8 | 1991 | DLT III | ||
| DLT2000 / TK87 | 10 | Fast SCSI-2 | 1.25 | 1993 | DLT III | ||
| DLT2000XT | 15th | Fast SCSI-2 | 1.25 | 1995 | DLT IIIXT | ||
| DLT4000 / TK88 | 20th | 40 | Fast SCSI-2 | 1.5 | 1994 | DLT IV | |
| DLT7000 / TK89 | 35 | 70 | Fast / Wide SCSI-2 | 5 | 1996 | DLT IV | |
| DLT8000 | 40 | 80 | Fast / Wide SCSI-2 | 6th | 1999 | DLT IV | |
| SDLT 220 | 110 | 220 | Ultra-2 | 10 | 1998 | SDLT I | |
| SDLT 320 | 160 | 320 | Ultra-2 | 16 | 2002 | SDLT I | |
| SDLT 600 | 300 | 600 | Ultra-160 / FC 2Gb | 36 | 72 | 2004 | SDLT II |
| SDLT 600A | 300 | 600 | GbE ( FTP , HTTP ) | 36 | 72 | 2005 | SDLT II |
| DLT-S4 | 800 | Ultra-320 / FC 4Gb / SAS | 60 | 2006 | S4 | ||
| DLT-S5 | 1500? | 100? | |||||
| Value line | |||||||
| DLT1 | 40 | Fast / Wide SCSI-2 | 3 | 1999 | DLT IV | ||
| DLT-VS80 | 40 | Fast / Wide SCSI-2 | 3 | 6th | 2001 | DLT IV | |
| DLT-VS160 | 80 | Ultra-2 | 8th | 16 | 2003 | VS1 | |
| DLT-V4 | 160 | Ultra-160 / SATA | 10 | 2005 | VS1 | ||
| DLT-V5 | 250? | 18? | |||||
| DLT-V7 | 3000 | 70 | |||||
media
| Surname | Formats | colour | supported by |
|---|---|---|---|
| CompacTape I | 0.1 | Gray | TK50 / 70 |
| CompacTape II | 0.3 | Gray | TK70 |
| DLTtape III | 2,6, 6, 10 | Light brown | DLT260 / 600, DLT2000 / 2000XT / 4000/7000 |
| DLTtape IIIXT | 15th | White | DLT2000XT / 4000/7000/8000 |
| DLTtape IV | 20, 35, 40 | Dark brown | DLT4000 / 7000/8000, DLT1, SDLT220 / 320 (ro) |
| Cleaning tape III | 20 cleans | beige | DLT2000 / 2000XT / 4000/7000/8000 |
| SDLTtape I | 110, 160 | Dark green | SDLT220 / 320, SDLT600 (ro), DLT-S4 (ro) |
| SDLTtape II | 300 | Dark blue | SDLT600, DLT-S4 (ro) |
| DLTtape S4 | 800 | Dark purple | DLT-S4 |
| SDLT cleaning tape | 20 cleans | Light gray | SDLT220 / 320/600, DLT-S4 |
| DLTtape VS1 | 80, 160 | Ivory / black | VS160, DLT-V4, SDLT600 (ro) |
| DLT VS Cleaning Tape | 20 cleans | brown | DLT1, DLT-VS80 |
| DLT VS160 cleaning tape | 20 cleans | Light gray with black flap | DLT-VS160, DLT-V4 |
Depending on the drive used, the capacity may vary (for example, a DLT-8000 drive can write 40 GB to a DLT-IV tape, a DLT-7000 drive can only write 35 GB, and a DLT-4000 drive only 20 GB ). Drives for DLT-III and DLT-IV media are for the most part backwards compatible with one another. SDLT drives can only read DLT-IV media, not write to them. DLT-III media can no longer be read with SDLT drives.
DLT media
DLT media contains a 1/2 inch (12.7 millimeter) wide magnetic tape that is encapsulated in a cartridge . The use of the DLT and SDLT logos (trademarks) has only been licensed by Quantum (for a fee) to companies 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 is held by Fujifilm. DLT media are considered reliable and well suited for long-term archiving , as they should only lose about 5 percent of their magnetization in 30 years.
In October 2001, the media manufacturer Imation sued Quantum for violating antitrust law, as Quantum only licensed the DLT / S-DLT trademark rights to certain companies and allegedly demanded excessive license fees for them. The US court dismissed Imation's complaint and ruled that the company had to transfer 30 percent of its income from the sale of DLT media to Quantum as license fees. After pressure from the court, an agreement was reached and Imation is now (again) the third tape and DLT cassette manufacturer worldwide.
Restoration of old tapes
Although the tapes from the manufacturers should guarantee data security for at least 30 years, they can practically no longer be read today. This is because the magnetic tapes oxidize over time. Even if the tapes are removed and cleaned, they contaminate the read head again when they are read, so that a reading process hardly seems possible.
Former employees of the software company Magnetic Scrolls are trying to restore old source code from TK50 tapes in 2018. In this context, by trying and losing some of the tapes, they found a way how oxidized and therefore no longer legible tapes can be read out again. However, this requires a functioning TZ30 drive and complex measures, such as. B. drying the tapes in the oven for 8 hours at exactly 45 degrees Celsius. The drive must also be opened during the reading process and the read head cleaned.
See also
- Generic terms: tape drive , data backup
- Tape drives: AIT , DAT , S-DLT, LTO , Mammoth , SLR , Travan , VXA
Individual evidence
- ↑ http://www.quantum.com/de
- ↑ Andreas Donath: Imation is suing Quantum over antitrust concerns . golem.de. October 4, 2001. Retrieved March 13, 2019.
- ↑ Christian Kruggel: Quantum sued for monopoly formation in DLT media . Heise online. October 2, 2001. Retrieved March 13, 2019.
- ↑ Andreas Donath: The court decides in the DLT dispute in favor of Quantum . golem.de. November 1, 2001. Retrieved March 13, 2019.
- ↑ Blog entry describing a restore process . strandgames.com. June 19, 2018. Retrieved August 1, 2019.
