Technology
DLT uses linear serpentine recording with multiple tracks on half-inch (12.7 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 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 1⁄2-inch-wide (13 mm) tape are available.
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 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 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, 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.
DLT includes Write Once Read Many (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.
Read more about this topic: Digital Linear Tape
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