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I found a hint to configure the st module in a mail from 2004 redhat mailinglist about a slow LTO-2 drive.

modprobe st buffer_kbs=1024 max_buffers=128 max_sg_segs=128 blocking_open=1

Are similar settings required for best performance of LTO-6 drives too? Where do we know the values from? What are the default settings, if no values are passed?

Jonas Stein
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  • What can make a difference is the block-size your software reading/writing the tape is using and the amount of eof-marks you write. Setting kernel parameters isn't required for optimal performance these days. – Andreas Rogge Feb 13 '19 at 21:57

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Are similar settings required for best performance of LTO-6 drives too?

Do you experience bad performance or is the speed not as expected? If no, just stick to the defaults. Otherwise ask the vendor or give more details about your LTO-6 drive.

Where do we know the values from?

Well, best would be to ask your hardware vendor or check on the manufacturer site and manual for your drive. Lastly you could just trail-n-error, if you experience bad performance.

What are the default settings, if no values are passed?

Look through dmesg and use modinfo st to reveal the possible values and defaults. You also could look at /sys/module/st/parameters/* to see the current settings. Might be that this is not available.

Thomas
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  • @JonasStein Is the drive used for writing to new tapes? Or is it used for overwriting previously used tapes? – kasperd Jul 30 '17 at 17:48
  • @kasperd it is used for brand new and used tapes. But how does it make a difference? – Jonas Stein Jul 30 '17 at 19:39
  • @JonasStein New tapes cause much wear on the heads and can lead to reduced capacity and performance. Here I am speaking from experience with LTO-4 tapes. I don't know if that has changed in later generations. – kasperd Jul 30 '17 at 21:37
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    @JonasStein do you mean "brakes" as in the drive stops and has to restart (aka "shoeshining"), or "breaks" as in the drive is now broken? – Dan Pritts Jul 31 '17 at 16:24
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    The reason is indeed that I am debugging, why the tape drive brakes (stops) so often. The provided data rate should be more than fast enough. But there could be a problem with the bus or the kernel (module) settings. I expected that all LTO-6 drives need the same parameters. /sys/module/st/parameters/* is not available here. – Jonas Stein Aug 01 '17 at 11:45