One of the most significant of the new formats is the next generation of Digital Linear Tape (DLT), otherwise known as Super DLT. This is important because developer Quantum accounted for around 80% of the tape drive market by early 1999. Drives based on Super DLT technology will far exceed the 35GB native capacity of the DLTtape IV format – with which it aims to be backwards compatible.

Using a combination of optical and magnetic recording techniques known as Laser Guided Magnetic Recording (LGMR) Super DLT uses lasers to more precisely align the recording heads. At the core of LGMR is an optically assisted servo system referred to as Pivoting Optical Servo (POS). This combines high-density magnetic read/write data recording with laser servo guiding. Designed for high duty cycle applications, the POS has a much lower sensitivity to external influences, which allows a much track density than is possible with other tape systems. The POS system decreases manufacturing costs and increases user convenience by eliminating the need for preformatting the tape. Furthermore, 10-20% more capacity is gained by deploying the optical servo on the unused backside of the media, making the entire recording surface available for actual data.

As the media moves through the POS, the optical tracking laser follows along on the backside of the media, tracking the embedded optical targets. The POS assembly pivots around a single mounting point to keep the magnetic read/write heads aligned with the optical tracks and reading data from or writing data to the tape. Another technological advance is the application of an advanced form of the Partial Response Maximum Likelihood (PRML) – a technique more usually associated with hard disk drives – to linear tape technology. This both further increases capacity and boosts data transfer rates by providing high encoding efficiency recording densities.

As indicated by the following table, the ultimate goal is to cram up to 1.2TB of uncompressed data onto a single cartridge with transfer rates rising to an eventual 100MBps uncompressed. Initial products, however, offer a more modest 110GB with sustained data transfer rates of 11MBps in native mode:

SDLT

220

SDLT

320

SDLT

640

SDLT

1280

SDLT

2400

Native Capacity 110GB 160GB 320GB 640GB 1.2TB
Compressed Capacity

(2:1 compression)

220GB 320GB 640GB 1.28TB 2.4TB
Native DTR 11MBps 16MBps 32MBps 50+MBps 100+MBps
Compressed DTR 22MBps 32MBps 64MBps 100+MBps 200+MBps
Media SDLT I SDLT I SDLT II SDLT III SDLT IV
Interfaces Ultra2 SCSI

LVD

HVD

Ultra2 SCSI

Ultra160 SCSI

Ultra 320 SCSI

Fibre channel

TBD TBD
Date Q1 2001 Q1 2002 Q3 2003 Q1 2005 Q3 2006

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