Digital Linear Tape (DLT) (previously called
CompacTape) is a
magnetic tape data storageMagnetic tape has been used for data storage for over 50 years. In this time, many advances in tape formulation, packaging, and data density have been made. Modern magnetic tape is most commonly packaged in cartridges and cassettes. The device that performs actual writing or reading of data is a...
technology developed by
Digital Equipment CorporationDigital Equipment Corporation was a pioneering American company in the computer industry. It is often referred to within the computing industry as DEC...
(DEC) from 1984 onwards. In 1994 the technology was purchased by Quantum Corporation, who currently manufactures drives and licenses 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.
Digital Linear Tape (DLT) (previously called
CompacTape) is a
magnetic tape data storageMagnetic tape has been used for data storage for over 50 years. In this time, many advances in tape formulation, packaging, and data density have been made. Modern magnetic tape is most commonly packaged in cartridges and cassettes. The device that performs actual writing or reading of data is a...
technology developed by
Digital Equipment CorporationDigital Equipment Corporation was a pioneering American company in the computer industry. It is often referred to within the computing industry as DEC...
(DEC) from 1984 onwards. In 1994 the technology was purchased by Quantum Corporation, who currently manufactures drives and licenses 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.
History
DEC launched the TK50 tape drive for the
MicroVAX IIThe MicroVAX is a family of low-end minicomputers developed and manufactured by Digital Equipment Corporation . The first model, the MicroVAX I, was introduced in 1984...
minicomputerA minicomputer is a class of multi-user computers that lies in the middle range of the computing spectrum, in between the largest multi-user systems and the smallest single-user systems...
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 The TK50 was superseded in 1987 by the TK70 drive and the 48-track CompacTape II cartridge, capable of storing 294 MB.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 improved the data density of the DLTtape III cartridge into the early 1990s, 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 310 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
reelA reel is an object around which lengths of another material are wound for storage. Generally a reel has a cylindrical core and walls on the sides to retain the material wound around the core...
and the
tapeMagnetic tape is a medium for magnetic recording generally consisting of a thin magnetizable coating on a long and narrow strip of plastic. Nearly all recording tape is of this type, whether used for recording audio or video or for computer data storage. It was originally developed in Germany,...
is pulled out of the cartridge by means of a leader tape attached to the takeup 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
capstanCapstans are rotating spindles used to move recording tape through the mechanism of a tape recorder. The tape is threaded between the capstan and one or more rubber-covered wheel, called a "pinch roller", which presses against the capstan, thus providing friction necessary for the capstan to pull...
. 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 servoVisual Servoing, also known as Vision Based Robot Control and abbreviated VS, is a technique which uses feedback information extracted from a vision sensor to control the motion of a robot. One of the earliest papers that talks about visual servoing was from the SRI International Labs. The most...
system that reads servo patterns on the back of the tape, in order 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 half inch wide tape are now common.
DLT7000 and 8000 tilt the head forward and backward to reduce crosstalk between adjacent tracks through
azimuthAn Azimuth is the angle from a reference vector in a reference plane to a second vector in the same plane, pointing toward, , something of interest. For example, with the sea as your reference plane, the azimuth of the Sun might be the angle between due North and the point on the horizon the Sun...
; this is called
Symmetric Phase RecordingTape recording 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 = /////, track 2 = \\\\\, track 3 = /////, etc....
.
All (S)DLT drives support hardware
data compressionIn computer science and information theory, data compression or source coding is the process of encoding information using fewer bits than an unencoded representation would use, through use of specific encoding schemes.As with any communication, compressed data communication only works when both...
. The often-used compression factor of 2:1 is optimistic and generally only achievable for text data; a more realistic factor across a file system is 1.3:1 to 1.5:1. Note that 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 under specified environmental conditions; however, they are easily damaged by mishandling (dropping or improper packaging during shipment.)
Current manufacturers of cartridges for the DLT/SDLT market are
Fujifilmis a Japanese company known for its photographic film and cameras. Fujifilm is the world’s largest photographic and imaging company. Fuji operates 223 subsidiary companies for research, manufacture and distribution of products, with manufacturing facilities in Asia, Europe, and the United States of...
, Hitachi/
Maxell, or Maxell, is a Japanese company which manufactures consumer electronics. The company's notable products are batteries and electronics -- the company's name is a contraction of "maximum capacity dry cell" -- and recording media, including audio cassettes and blank VHS tapes, and recordable...
and
ImationImation is a US based multi-national corporation that designs, manufactures, sources or markets a wide range of recordable data storage media and consumer electronics products.The company is a 1996 spin off of 3M and is headquartered in Oakdale, Minnesota...
. VStape is made by
Sonyis a multinational conglomerate corporation headquartered in Minato, Tokyo, Japan, and one of the world's largest media conglomerates with revenue exceeding ¥ 7.730.0 trillion, or $78.88 billion U.S. . Sony is one of the leading manufacturers of electronics, video, communications, video game...
. 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 ManyWrite Once, Read Many refers to computer data storage systems, data storage devices, and data storage media that can be written to once, but read from multiple times....
(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
LTOLinear Tape-Open is a magnetic tape data storage technology originally developed in the late 1990s as an open standards alternative to the proprietary magnetic tape formats that were available at the time. Seagate, Hewlett-Packard, and IBM initiated the LTO Consortium, which directs development...
.
Drives
| Drive |
Capacity (GB) |
Interface |
Data Rate (MB/s) |
Date |
Media |
| TK50/TZ30 |
0.1 |
proprietary/SCSI |
0.045 |
1984 |
CT I |
| TK70 |
0.3 |
proprietary |
0.045 |
1987 |
CT II |
| THZ01/DLT260/Tx85 |
2.6 |
DSSI The Digital Storage Systems Interconnect is a bus developed by Digital Equipment Corporation for connecting storage devices and clustering VAX systems. It was introduced in 1988. The bus has a bandwidth of 32 Mbit/s and was typically limited to a length of 25 meters....
/SCSISmall Computer System Interface, or SCSI , is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces...
|
0.8 |
1989 |
DLT III |
| THZ02/DLT600/Tx86 |
6 |
DSSI The Digital Storage Systems Interconnect is a bus developed by Digital Equipment Corporation for connecting storage devices and clustering VAX systems. It was introduced in 1988. The bus has a bandwidth of 32 Mbit/s and was typically limited to a length of 25 meters....
/SCSISmall Computer System Interface, or SCSI , is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces...
|
0.8 |
1991 |
DLT III |
| DLT2000/Tx87 |
10 |
Fast SCSI-2 |
1.25 |
1993 |
DLT III |
| DLT2000XT |
15 |
Fast SCSI-2 |
1.25 |
1995 |
DLT IIIXT |
| DLT4000/Tx88 |
20 |
Fast SCSI-2 |
1.5 |
1994 |
DLT IV |
| DLT7000/Tx89 |
35 |
Fast/Wide SCSI-2 |
5 |
1996 |
DLT IV |
| DLT8000 |
40 |
Fast/Wide SCSI-2 |
6 |
1999 |
DLT IV |
| SDLT 220 |
110 |
Ultra-2-Wide SCSI |
10 |
1998 |
SDLT I |
| SDLT 320 |
160 |
Ultra-2-Wide SCSI |
16 |
2002 |
SDLT I |
| SDLT 600 |
300 |
Ultra-160 SCSI/FCFibre Channel, or FC, is a gigabit-speed network technology primarily used for storage networking. Fibre Channel is standardized in the T11 Technical Committee of the InterNational Committee for Information Technology Standards , an American National Standards Institute –accredited standards...
2Gb |
36 |
2004 |
SDLT II |
| SDLT 600A |
300 |
GbEGigabit Ethernet is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second, as defined by the IEEE 802.3-2008 standard...
(FTPFile Transfer Protocol is a standard network protocol used to exchange and manipulate files over a TCP/IP based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server applications...
, HTTP) |
36 |
2005 |
SDLT II |
| DLT-S4 |
800 |
Ultra-320 SCSI/FCFibre Channel, or FC, is a gigabit-speed network technology primarily used for storage networking. Fibre Channel is standardized in the T11 Technical Committee of the InterNational Committee for Information Technology Standards , an American National Standards Institute –accredited standards...
4Gb/SASIn computing, the data-transfer technology Serial Attached SCSI moves data to and from computer storage devices such as hard drives and tape drives. SAS depends on a point-to-point serial protocol that replaces the parallel SCSI bus technology that first appeared in the mid 1980s in data centers...
|
60 |
2006 |
S4 |
| DLT-S4A |
800 |
GbEGigabit Ethernet is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second, as defined by the IEEE 802.3-2008 standard...
(FTPFile Transfer Protocol is a standard network protocol used to exchange and manipulate files over a TCP/IP based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server applications...
, HTTP) |
60 |
2007 |
S4 |
| Value line |
| DLT1 |
40 |
Fast/Wide SCSI-2 |
3 |
1999 |
DLT IV |
| DLT-VS80 |
40 |
Fast/Wide SCSI-2 |
3 |
2001 |
DLT IV |
| DLT-VS160 |
80 |
Ultra-2-Wide SCSI |
8 |
2003 |
VS1 |
| DLT-V4 |
160 |
Ultra-160 SCSI/SATAThe serial ATA, or SATA computer bus, is a storage-interface for connecting host bus adapters to mass storage devices such as hard disk drives and optical drives. The SATA host adapter is integrated into almost all modern consumer laptop computers and desktop motherboards.Serial ATA was designed...
USB |
10 |
2005 |
VS1 |
Media
| Name |
Formats (GB) |
Color |
Supported by (ro=read only) |
| CompacTape I |
0.1 |
Gray |
TK50/TZ30, TK70 (ro) |
| CompacTape II |
0.3 |
Gray |
TK70 |
| DLTtape III |
2.6, 6, 10 |
Light brown |
DLT260/600, DLT2000/2000XT/4000/7000 |
| DLTtape IIIXT |
15 |
White |
DLT2000XT/4000/7000/8000 |
| DLTtape IV |
20, 35, 40, 80 |
Dark brown |
DLT4000/7000/8000, 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 |
DLT-VS160, DLT-V4 |
Tapes written in value series drives can typically be read (and often written) in higher end drives of a similar vintage. The drive's technical specifications should contain interoperability options.
External links
Standards