Digital Linear Tape (DLT; previously called CompacTape) is a

magnetic-tape data storage Magnetic-tape data storage is a system for storing digital information on magnetic tape using digital recording. Tape was an important medium for primary data storage in early computers, typically using large open reels of 7-track, later ...

technology developed by

Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president until ...

(DEC) from 1984 onwards. In 1994, the technology was purchased by

Quantum Corporation Quantum Corporation is a data storage, management, and protection company that provides technology to store, manage, archive, and protect video and unstructured data throughout the data life cycle. Their products are used by enterprises, media ...

, who manufactured drives and licensed the technology and trademark. A variant with higher capacity is called Super DLT (SDLT). The lower cost "value line" was initially manufactured by Benchmark Storage Innovations under license from Quantum. Quantum acquired Benchmark in 2002. In 2007, Quantum stopped developing DLT drives, shifting its strategy to LTO.

History

DEC launched the TK50 tape drive for the MicroVAX II and

PDP-11 The PDP–11 is a series of 16-bit minicomputers originally sold by Digital Equipment Corporation (DEC) from 1970 into the late 1990s, one of a set of products in the Programmed Data Processor (PDP) series. In total, around 600,000 PDP-11s of a ...

minicomputer A minicomputer, or colloquially mini, is a type of general-purpose computer mostly developed from the mid-1960s, built significantly smaller and sold at a much lower price than mainframe computers . By 21st century-standards however, a mini is ...

s in 1984. This used 22-track CompacTape I cartridges, storing 94 MB per cartridge. The TK50 was superseded in 1987 by the TK70 drive and the 48-track CompacTape II cartridge, capable of storing 294 MB. In 1989, the CompacTape III (later DLTtape III) format was introduced, increasing the number of tracks to 128 and capacity to 2.6 GB. Later drives into the early 1990s improved the data density of the DLTtape III cartridge, up to 10 GB. The DLTtape IV cartridge was introduced by Quantum in 1994, with increased tape length and data density, initially offering 20 GB per tape. Super DLTtape, originally capable of up to 110 GB, was launched in 2001.

Technology

DLT uses linear serpentine recording with multiple tracks on half-inch (12.7 mm) wide tape. The cartridges contain a single

reel A reel is a tool used to store elongated and flexible objects (e.g. yarns/ cords, ribbons, cables, hoses, etc.) by wrapping the material around a cylindrical core known as a '' spool''. Many reels also have flanges (known as the ''rims'') arou ...

and the tape is pulled out of the cartridge by means of a leader tape attached to the take-up reel inside the drive. The drive leader tape is buckled to the cartridge leader during the load process. Tape speed and tension are controlled electronically via the reel motors; there is no capstan. The tape is guided by 4 to 6 rollers that touch only the back side of the tape. Tape material is metal particle tape (MP/AMP). SDLT adds an optical servo system that reads servo patterns on the back of the tape to keep the data tracks on the front of the tape correctly aligned with the read/write heads. This is important for newer tape media, which have very thin, dense data tracks; 256, 384 and 768 data tracks on a tape are available. DLT7000 and 8000 tilt the head forward and backward to reduce crosstalk between adjacent tracks through

azimuth An azimuth (; from ) is the horizontal angle from a cardinal direction, most commonly north, in a local or observer-centric spherical coordinate system. Mathematically, the relative position vector from an observer ( origin) to a point ...

; this is called

Symmetric Phase Recording Symmetric Phase Recording is a tape recording ( computer storage media) technology developed by Quantum Corporation packs data across a tape's recording surface by writing adjacent tracks in a herringbone pattern: track 0 = \\\\\, track 1 = /////, ...

. All (S)DLT drives support hardware

data compression In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compressi ...

. The often-used compression factor of 2:1 is optimistic and generally only achievable for text data; a more realistic factor for a file system is 1.3:1 to 1.5:1, although drive compression applied to pre-compressed data can actually make the written data larger than having compression turned off in the tape drive. Media are guaranteed for 30 years of

data retention Data retention defines the policies of persistent data and records management for meeting legal and business data archival requirements. Although sometimes interchangeable, it is not to be confused with the Data Protection Act 1998. The differe ...

under specified environmental conditions; they are easily damaged by mishandling (dropping or improper packaging during shipment.) Manufacturers of cartridges for the DLT/SDLT market are

Fujifilm , trading as , or simply Fuji, is a Japanese Multinational corporation, multinational Conglomerate (company), conglomerate headquartered in Tokyo, Japan, operating in the areas of photography, optics, Office supplies, office and Biomedical engine ...

, Hitachi/

Maxell , commonly known as Maxell, is a Japanese company (law), company that manufactures consumer electronics. The company's name is a contraction of "Maximum capacity dry cell". Its main products are Battery (electricity), batteries, wireless chargi ...

and Imation. VStape is made by

Sony is a Japanese multinational conglomerate (company), conglomerate headquartered at Sony City in Minato, Tokyo, Japan. The Sony Group encompasses various businesses, including Sony Corporation (electronics), Sony Semiconductor Solutions (i ...

. All other companies/brands (even Quantum) are contractors and/or resellers of these companies. A new naming convention took effect in 2005, calling the performance line DLT-S and the value line DLT-V. DLT includes

Write Once Read Many Write once read many (WORM) describes a data storage device in which information, once written, cannot be modified. This write protection affords the assurance that the data cannot be tampered with once it is written to the device, excluding the ...

(WORM) capability.. In February 2007, Quantum stopped developing the next generations of DLT drives (S5 and V5) after insufficient market acceptance of the S4 and V4 drives, shifting its drive strategy to LTO.

Generations

Drives

Media

DLTtape IV can support both DLT4000/7000/8000 and DLT1/DLT-VS80 for full functions; once DLTtape IV media has been written to or formatted in a DLT7000/8000 drive, this media cannot be read, written to, or formatted in a DLT1/DLT-VS80 drive unless it is degaussed. Once the media has been written to or formatted in a DLT4000 drive, the media cannot be written to or formatted in a DLT1/DLT-VS80 drive unless it is degaussed but it can be read. This is because the DLT1/VS series use a different recording format that is not fully supported by the other family. Tapes written in value series drives can typically be read in (and often written to) higher end drives of a similar vintage, so long as the drive's technical specifications contain interoperability options.

References

External links

* . * at
Obituary
of Dr. Fred Hertrich, "father" of DLT

Standards

Specification of DLT 2

ECMA 209
Specification of DLT 3

ECMA 231
Specification of DLT 4

ECMA 258
Specification of DLT 3-XT

ECMA 259
Specification of DLT 5

ECMA 286
Specification of DLT 6

ECMA 320
Specification of SDLT-1

{{Digital Equipment Corporation DEC hardware Computer storage tape media Ecma standards