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SLR to the rescue?

The past, present and future of ADR and SLR tape formats.

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This Techworld document tabulates details of the ADR and SLR tape formats and includes road map details where available.

ADR
This is an OnStream (ex-Philips subsidiary) format, standing for Advanced Digital Recording, aimed at the DDS market. ADR1 was the first generation with its ADR 30 and ADR 50 formats. ADR2.n is the second generation. OnStream went bankrupt in May this year and it looks as if the format has no future. For your reference the format details are:

  ADR 30 ADR 50 ADR2.60 ADR2.120
Raw Capacity c15GB c25GB 30GB 60GB
Compressed Capacity 30GB 50GB 60GB 120GB
Raw Transfer Rate     to 4MB/sec to 4MB/sec
Compressed Transfer Rate to 4MB/sec to 4MB/sec to 8MB/sec to 8MB/sec
Date available c1999 Ic1999 2001 2001
Notes     Reads/writes 8 tracks at once  

ADR2.n has IDE, SCSI or USB2 connectivity. There is a mid-tape directory to reduce access times. ADR2 drives have heads with half the track width of the previous generation, allowing twice the capacity on the same amount of tape. Enhancements to the servo system ensured that the thin film heads followed the tracks on the tape media accurately. OnStream Data recovered from bankruptcy in 2001 with an injection of private capital and became Onstream Data BV, based in the Netherlands. This company has now failed, declaring the Dutch version of Chapter 11 in May this year, signalling a possible consolidation in the low end tape market. Users with ADR drives now need to look ahead for a migration target. SLR might well be a possible destination.

SLR
A Tandberg proprietary linear tape format SLR, standing for Scalable Linear Recording, is positioned as a Travan and DDS alternative. It is very scalable with eight existing generations and two further generations proposed in a roadmap. SCSI connectivity is characteristic of each format. Tandberg is Quantum's manufacturing partner for SDLT drives and has a long track record as a tape drive manufacturer. SLR3 and 4 formats are no longer actively marketed by Tandberg.

  SLR3 SLR4 SLR5
Raw Capacity 1.2GB 2.5GB 4GB
Compressed Capacity   5GB 8GB
Raw Transfer Rate 300KB/sec 300KB/sec 380KB/sec
Compressed Transfer Rate   600KB/sec 560KB/sec

SLR7, 50, 60, 100 and 140 formats use 0.315 inch tape media, which has 26 per cent more recording area than the previous SLR3, 4 and 5 formats. Using a PRML (Partial Response Maximum Likelihood) recording method about 50 per cent more data can be written onto the recordable area. There are 192 data tracks on the SLR60, 100 and 140 formats, but only 72 on the SLR7 format.

  SLR7 SLR50 SLR60 SLR100
Raw Capacity 20GB 25GB 30GB 50GB
Compressed Capacity 40GB 50GB 60GB 100GB
Raw Transfer Rate 3MB/sec 2MB/sec 4MB/sec 5MB/sec
Compressed Transfer Rate 6MB/sec 4MB/sec 8MB/sec 10MB/sec
SLR140 was announced in September, 2003. It had been called SLR150 previously, implying a compressed capacity of 150GB. In the event it reached 140GB. The roadmap shows two further generations. The planned SLR200 and SLR400 capacity targets are just that; targets, and may not be fully realised.
  SLR140 SLR200 SLR400
Raw Capacity 70GB 100GB 200GB
Compressed Capacity 140GB 200GB 400GB
Raw Transfer Rate 6MB/sec 16MB/sec 32MB/sec
Compressed Transfer Rate 12MB/sec 32MB/sec 64MB/sec
Date Available 2003 2004? 2005/6

SLR140 is backwards compatible with all previous SLR formats except SLR3, 4 and 5.


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