Digital Linear Tape

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Digital Linear Tape (DLT) is a magnetic tape technology used for computer data storage. It was invented by Digital Equipment Corporation in 1984, and was purchased by Quantum Corporation in 1994, 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. Quantum acquired Benchmark in 2002.

Contents 1 Technology 2 Generations 2.1 Drives 2.2 Media 3 External links 3.1 Standards

[edit] Technology

DLT uses linear serpentine recording with multiple tracks on half-inch (12.6 mm) wide tape. The cartridges contain a single reel and the tape 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 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, 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 azimuth; this is called Symmetric Phase Recording.

All (S)DLT drives support hardware data compression. 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.

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 Fujifilm, Hitachi/Maxell and Imation. VStape is made by Sony. 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.

[edit] Generations

[edit] Drives

Standard	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	1989	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	10	1998	SDLT I
SDLT 320	160	Ultra-2	16	2002	SDLT I
SDLT 600	300	Ultra-160/FC 2Gb	36	2004	SDLT II
SDLT 600A	300	GbE (FTP, HTTP)	36	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	2001	DLT IV
DLT-VS160	80	Ultra-2	8	2003	VS1
DLT-V4	160	Ultra-160/SATA	10	2005	VS1
DLT-V5	250?		18?

[edit] Media

Name	Formats	Color	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	15	White	DLT2000XT/4000/7000/8000
DLTtape IV	20, 35, 40	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. Check the specs for your specific drive to find out its interoperability options.

[edit] External links

• History of DLTtape™ Technology, from TK50 1984 to SDLT1 2001
• DLTtape™ Handbook, 8th ed. (Quantum 2001) (PDF)
• DLT Roadmap at dlttape.com
• Quantum Corp. DLT drive page
• Obituary of Dr. Fred Hertrich, "father" of DLT

[edit] Standards

• ECMA 197 Specification of DLT 2. [1]
• ECMA 209 Specification of DLT 3. [2]
• ECMA 231 Specification of DLT 4. [3]
• ECMA 258 Specification of DLT 3-XT. [4]
• ECMA 259 Specification of DLT 5. [5]
• ECMA 286 Specification of DLT 6. [6]
• ECMA 320 Specification of SDLT-1. [7]

view • talk • edit	Magnetic tape data storage formats
	Linear	Helical-Scan
Three Quarter Inch (~19 mm)	LINCtape (1962) - DECtape (1963)	Sony DIR (19xx) - Ampex DST (1992)
Half Inch (12.65 mm)	UNISERVO (1951) - IBM 7 Track (1952) - IBM 9 Track (1964) - IBM 3480 (1984) - DLT (1984) - IBM 3590 (1995) - T9840 (1998) - T9940 (2000) - LTO Ultrium (2000) - T10000 (2006)	Redwood SD-3 (1995) - DTF (19xx) - SAIT (2003)
Eight Millimeter (8 mm)	Travan (1995) - IBM 3570 MP (1997)	Exabyte (1987) - Mammoth (1994) - AIT (1996) - VXA (1999)
Quarter Inch (6.35 mm)	QIC (1972) - SLR (1986)
Four Millimeter (3.8 mm)	DC100 (1976) - DECtapeII (1979)	DDS/DAT (1989)
One Eighth Inch (3.18 mm)	KC Standard, Compact Cassette (1975) - Datassette (1977)
Stringy (1.58 - 1.9 mm)	Exatron Stringy Floppy (1979) - ZX Microdrive (1983) - Rotronics Wafadrive (1984)