Super DLT (SDLT) is a backward compatible improvement of DLT. SDLT technology can store up to 300 gigabytes of uncompressed data, or up to 600 gigabytes with 2:1 data compression. This large storage capacity makes SDLT ideal for storing, archiving and backing up large volumes of information.

DLT stands for Digital Linear Tape. Tape storage developed in the late seventies by Digital Equipment Corporation (DEC) in 1984, and the basis for successive generations of DLT tape drive which higher storage capacities and transfer rates. Most DLT drives are backwards compatible but this is not guaranteed, so check. A variant with higher capacity is called Super DLT (SDLT). DLT tapes use half inch tape media, fully enclosed in a sealed case which is designed only to open when the tape is in the drive.

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.

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.

Capacity

Drives

Media

Notes:

1. Native capacity is with no compression applied.
2. Notional capacity is with hardware compression applied. Quoted figures normally assume a compression ratio of 2:1 but this will vary with real data.
3. Drives are often quoted with a "Notional backup rate", which is the rate at which data can be written to the tape with an assumed 2:1 compression ration. The notional backup rate is therefore double the native backup rate.

See also: DDS, LTO, DLT, SDLT, AIT, QIC, 8mm, Travan, Optical, DVD-RAM

Additional Info From Other Sites:

• 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

Low Level Specifications:

• ECMA 197 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