Digital Linear Tape
| Company type | Technology / Data storage system |
|---|---|
| Industry | Data storage |
| Predecessor | CompacTape |
| Founded | 1984 |
| Founder | Digital Equipment Corporation (DEC) |
| Fate | Technology taken over by Quantum Corporation in 1994; discontinued development in 2007 |
| Successor | LTO technology (by Quantum Corporation) |
Area served | Worldwide |
| Products | Magnetic tape data storage systems, DLT drives, Super DLT (SDLT) |
Digital Linear Tape (DLT; originally known as CompacTape) is a magnetic tape-based data storage system first developed by Digital Equipment Corporation (DEC) beginning in 1984. In 1994, Quantum Corporation took over the technology, producing drives and managing the trademark licensing. An enhanced version with greater capacity is known as Super DLT (SDLT). The more affordable "value line" was initially manufactured by Benchmark Storage Innovations under license from Quantum; Quantum later acquired Benchmark in 2002.
By 2007, Quantum discontinued further development of DLT drives, redirecting efforts toward LTO technology.
History
In 1984, DEC introduced the TK50 tape drive designed for MicroVAX II and PDP-11 minicomputers, utilizing 22-track CompacTape I cartridges with a storage capacity of 94 MB. This was followed in 1987 by the TK70 and the 48-track CompacTape II, which offered 294 MB of storage. The 1989 release of CompacTape III (later called DLTtape III) expanded track count to 128 and boosted capacity to 2.6 GB, later enhanced to 10 GB during the early 1990s. Quantum unveiled DLTtape IV in 1994, featuring longer tape length and increased density, initially providing a capacity of 20 GB per tape. The Super DLTtape series launched in 2001, offering capacities up to 110 GB.
Technology
DLT technology utilizes linear serpentine recording on half-inch (12.7 mm) wide tape with multiple data tracks. Each cartridge houses a single reel; the tape is extended out via a leader tape connected to the drive’s take-up reel. Tape speed and tension are managed electronically by motors on the reels without employing a capstan mechanism. Guidance rollers make contact solely with the tape’s reverse side; the media employs metal particle (MP/AMP) tapes.
The SDLT format integrates an optical servo system that reads encoded patterns on the tape’s backside to ensure accurate track positioning, enabling a high density of up to 768 tracks on half-inch tape.
Models such as DLT7000 and DLT8000 utilize Symmetric Phase Recording technology, which involves tilting read/write heads to minimize crosstalk between adjacent tracks by adjusting azimuth angles.
All (S)DLT drives offer hardware-based data compression; typical compression ratios observed in practical use range between 1.3:1 and 1.5:1, with theoretical maximum compression near 2:1 for text files. Compression applied to already compressed data may result in increased file size.
The media are warranted to retain data integrity for up to 30 years under proper storage conditions but remain susceptible to physical damage caused by mishandling.
Primary cartridge manufacturers include Fujifilm, Hitachi/Maxell, and Imation, while Sony produces VStape media. Various other companies, including Quantum itself, act as resellers or contract manufacturers.
Starting in 2005, Quantum adopted a naming scheme distinguishing performance models as DLT-S and value models as DLT-V.
DLT technology supports Write Once Read Many (WORM) functionality.
Following limited commercial success of S4 and V4 series models, Quantum ceased advancement of next-generation DLT drives after 2007, shifting focus exclusively to LTO technology.
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/SCSI | 0.8 | 1991 | DLT III |
| THZ02/DLT600/Tx86 | 6 | DSSI/SCSI | 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 | 11 | 1998 | SDLT I |
| SDLT 320 | 160 | Ultra-2-Wide SCSI | 16 | 2002 | SDLT I |
| SDLT 600 | 300 | Ultra-160 SCSI/Fibre Channel 2Gb | 36 | 2004 | SDLT II |
| SDLT 600A | 300 | Gigabit Ethernet (FTP, HTTP) | 36 | 2005 | SDLT II |
| DLT-S4 | 800 | Parallel SCSI#Ultra-320 SCSI/Fibre Channel 4Gb/Serial Attached SCSI (SAS) | 60 | 2006 | S4 |
| DLT-S4A | 800 | Gigabit Ethernet (FTP, HTTP) | 60 | 2007 | S4 |
| Value line | |||||
| DLT1 | 40 | Fast/Wide Parallel SCSI#SCSI-2 (SCSI-2) | 3 | 1999 | DLT IV |
| DLT-VS80 | 40 | Fast/Wide Parallel SCSI#SCSI-2 (SCSI-2) | 3 | 2001 | DLT IV |
| DLT-VS160 | 80 | Parallel SCSI#Ultra-2 Ultra-2-Wide SCSI | 8 | 2003 | VS1 |
| DLT-V4 | 160 | Parallel SCSI#Ultra-3 Ultra-160 SCSI/Serial ATA/USB#USB_2.0 | 10 | 2005 | VS1 |
Media
| Name | Capacity (GB) | Colour | Compatible with (ro=read only) |
|---|---|---|---|
| CompacTape I | 0.1 | Light Grey | TK50/TZ30, TK70 (ro) |
| CompacTape II | 0.3 | Dark Grey | 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 | Dark Brown | DLT4000/7000/8000, DLT1/DLT-VS80, 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 Grey | 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 Grey | DLT-VS160, DLT-V4 |
The DLTtape IV format is fully functional with both the DLT4000/7000/8000 and the DLT1/DLT-VS80 systems; however, media created or formatted on DLT7000 or DLT8000 units are incompatible with DLT1/DLT-VS80 drives unless they undergo degaussing. Similarly, tapes prepared on a DLT4000 can be read but not written or formatted on a DLT1/DLT-VS80 without degaussing due to differing recording methods.
Generally, tapes from the value series retain compatibility with more advanced drives from the same era, provided the drive’s specifications support them.
See also
External links
- .
- at
- Obituary for Dr. Fred Hertrich, recognized as the "father" of DLT