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I have to compress 14 GB of csv files with 7zip. What options should I use to achieve the highest compression?

I have tried Ultra Level with both LZMA and PPMd compression method, obtaining results between 5% and 7%, but since I don't know how Dictionary and Word sizes work I was wondering if a better combination of options exists to reduce the compressed size around 500Mb.

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    what options have you tried already? What were the results? – Ƭᴇcʜιᴇ007 May 23 '14 at 17:54
  • This is very strange, with PPMd for text files I have compression levels over 90%, and you or anyone else should too. Your code depository must have some already compressed large binaries hiding somewhere in clear sight - perhaps some other 7z archive? – arch-abit May 23 '14 at 18:23
  • Opps, I misread csv for cvs, so it is not a code depository, but csv are still plain text files, so the rest of my assumptions still stand, adding that you might have the source database included in 7zip's working path. – arch-abit May 23 '14 at 18:32
  • @Giacomo Tesio - Even stranger is the fact that just by optional settings you managed to compress text files from 7% to over 90%. 7zip compression on text files is pretty consistent in around 20% variation range no matter what options you set or not set. The math here just do not add up. Could you please share with us what exactly was the issue, and what options did you use? I use 7zip at work in a number of production machines, and even 1% improvement would make a big difference for me. – arch-abit May 23 '14 at 18:51
  • No, I meant that I did obtain a compression around 5%-7% of the original size (from around 800MB to around 1G). – Giacomo Tesio May 23 '14 at 22:04
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You should use the "Ultra" setting. and leave the rest to defaults.

  • Thus defaults are optimized to produce the highest space indipendently of the time required for the compression? – Giacomo Tesio May 23 '14 at 17:53

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