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I have about 900 GB of uncompressed SQL dumps which have a very large amount of common data. I've been using 7z with the -mx=9 option because I care much more about the size of the archive than how long it takes to compress. That makes an archive around 42 GB.

I just discovered the options mfb, md, and ms. The man page doesn't tell me much about what those options do. What are fast bytes, dictionary size, and solid archive, and when would I want certain settings, especially in my case? The 7-Zip documentation says that level 9 compression has a dictionary of 64 MB. Since my archive is 42 GB, does it help to use a much larger dictionary? Under what circumstances is it useful to use non-default settings?

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    You can only benchmark different settings yourself. Preferably with a smaller dataset of course, but of similar contents.
    – Daniel B
    Aug 19, 2021 at 18:22
  • superuser.com/questions/616785/…
    – Keltari
    Aug 20, 2021 at 1:16
  • When it comes to things like compression, there is no known "best" scenario. Compression is going to depend entirely on the data being compressed and the algorithm being used.
    – Keltari
    Aug 20, 2021 at 1:23
  • @Keltari, I get that, which is why I specified the type of data. I'm using the default algorithm in 7z, if that wasn't clear. The answer you linked to explains what the dictionary is, but I haven't found good explanations of fast bytes and solid archive.
    – aswine
    Aug 20, 2021 at 16:08
  • @DanielB, yes, I could do a bunch of trial and error, but I was hoping someone could explain those options and why someone would choose particular settings for those options.
    – aswine
    Aug 20, 2021 at 16:09

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