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  • LTO6 transfer very slow

     Neil Sadwelkar updated 1 week ago 3 Members · 4 Posts
  • Terry Barnum

    January 6, 2021 at 3:14 am

    I’m backing up one of our QNAP NAS’s (thank you Bob Z) via 10GbE to an mLogic LTO6 connected over Thunderbolt3 on a new (intel) Mac Mini with Imagine’s MyLTO. Many of the media folders transferred sooooo much faster than our old LTO4, but some project folders are going really slowly. Like days. Literally. The only thing that’s different with these folders that I can see is they contain FCPX libraries. Since these FCPX libraries/packages contain so many small files, could this be what’s causing the slowdown? I also zipped the libraries in case the LTO backup mangles the raw libraries, but the time it’s taking to backup is unexpected. Any suggestions or is this just the way it is? I just emailed Imagine for their input.

  • Tim Jones

    January 6, 2021 at 5:58 pm

    Terry – you’re probably witnessing the delays caused by the input pipe of the LTO-6 running dry (underrrun) due to the QNAP coming over 1GbE (100+/- MB/sec). To properly stream an LTO-6, you need to be able to supply a sustained 200MB/sec minimum. Otherwise, the drive has to pause, wait for the input buffer to hit its high-water mark, reposition the tape, and then continue. Combine that with the fact that you can’t adjust the I/O buffer sizes with LTFS-based solutions and the result is a much, much overall slower task.

    With FCP projects containing lost of little files, this becomes even more apparent as it takes even more time to open, stat, read, and close each of those smaller files – further reducing the rate of data feeding the tape drive’s input buffers.

    LTO-7 and LTO-8 are worse since they need over 450MB/sec sustained input to properly stream.

    There really isn’t a way to speed things up unless you can bump your QNAP connection to 10GbE.

  • Terry Barnum

    January 6, 2021 at 7:23 pm

    Thank you very much for the reply Tim. The connection is via 10GbE through a 10GbE switch to the QNAP. The MacMini was ordered with 10GbE. Also, I mistyped last night, it’s an LTO-7 not an LTO-6.

    Imagine replied this morning that maybe the FCPX library contains “reference files or broken links that are causing copy/verification routine heartburn…” and to check the log file when complete to see if there are errors. I would think that if there were broken files/links the library wouldn’t open or FCPX would complain, which is not the case.


  • Neil Sadwelkar

    January 10, 2021 at 7:15 pm

    I don’t know if myLTO is the same as PreRoll Post, also from Imagine. I had a license of that, and had the same issue. It was dog slow backing up large file sequences like what one has from an Arri Alexa camera, or DNG from a drone. It used to be something to do with their database if I remember right.

    Bru-PE, Yoyotta, or Canister do a better job. I’ve used all three for file sequences. I’ve also used them with a QNAP connected over Thunderbolt3 or over 10GigE and they do not have this issue with folders with a large number of files.

    You can get a trial license of either, and try for yourself, with the exact same media.

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