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cyberax • today at 6:01 PM • 1 reply • view on HN

Yeah, the back-compat story for LTOs is not great. They are going to try and improve it starting with LTO-10.

It was partially on purpose for the earlier LTO generations. The capacity/speed ratio was not too high, so you could just keep upgrading your library in the background every decade. It outweighed the complexity of designing backwards-compatible hardware.

But it's becoming less practical now. LTO-4 is 1.6Tb with 160Mb read speed, so each tape takes just about 3 hours to read. LTO-10 is 40Tb with 400Mb read speed, resulting in more than 24 hours of time to read one tape.

Drive availability is an interesting question in itself. Laser drivers are pretty complicated beasts themselves that require highly precise mechanics. Tape drives are much simpler, because the areal information density is about 3 orders of magnitude smaller than on optical media.

The mechanical stuff that loads and unloads the tape and keeps it in tension is crazy, but it's all just regular "macroscopic" parts that can be custom-manufactured if needed.

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traceroute66 • today at 6:14 PM

> Tape drives are much simpler

Maybe back in the 90's :)

LTO-9 increased track density, increased the total number of tracks by reducing their width and increased linear density.

The "how" certainly does not sound "much simpler" to me ?[1]

    The new, narrower track width was achieved through a combination of improvements in tracking
    performance, new, narrower tunneling magnetoresistive (TMR) readers within the head assembly
    (now <1000nm in width) and optimized writers. The narrower tracks also necessitated
    improvements to the media magnetic layer. Magnetic particles are Barium Ferrite (BaFe) as in LTO-8, but with
    improved characteristics to support the higher linear densities.

    Changes were also made to the tape substrate, with the thickness reduced by 7% from 5.6µm to
    5.2 µm. This in turn enables more tape to fit on the reel – tape length per cartridge has
    increased from 960m to 1035m. The new substrate also features optimized stability
    characteristics to mitigate tape dimensional variations that occur due to fluctuations in
    environmental conditions.
In addition the LTO Program's own technical paper describes how LTO-9 manages dimensional changes in the new substrate with a one-time-per-tape calibration algorithm to control 32-channel recording via closed-loop servo algorithms, plus a longer-block Reed-Solomon C2 code — together getting LTO-9's uncorrectable bit error rate to 10⁻²⁰, a 10× improvement over LTO-8[2]

[1] https://at.ingrammicro.eu/api/cfs/Icecat/PDF.ashx?l=en&s=957... [2] https://www.lto.org/wp-content/uploads/2022/08/LTO-UBER-Tech...

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