7-zIp And Compression Noob

Help
Jay
2012-01-12
2012-12-07
  • Jay

    Jay - 2012-01-12

    Hi everyone,

    I'm completely new to the world of compression and I need a lot of help understanding the terms and how to use 7-zip.

    First could someone give me a clear definition of these terms and their functions:

    Compression Method

    Dictionary Size

    Word Size

    Solid Block Size

    Number Of CPU threads

    Encryption Method

    And for the second and last question.When you're compression a file larger than 1GB is it possible to speed up the process?

     
  • fernando

    fernando - 2012-01-12

    definition of these terms and their functions

    Review topics found at 'File Manager > Plugins > 7-Zip > Add to Archive Dialog Box' of the included help .CHM file.

     
  • Jay

    Jay - 2012-01-14

    Thanks for asking the first part of my question can someone answer this:

    I have a folder its size is: 1.58GB

    Here are the settings I'm using to compress:

    Archive Format: 7zip

    Compression Level: Maximum

    Compression Method: LZMA

    Dictionary Size: 16MB

    Word Size: 64

    Solid Block Size: 2GB

    Number Of CPU Threads: 1

    Update Mode: Add And Replace Files

    Encryption Method: AES-256

    Is there anyway I can change anyone of these settings so that I may speed up the process for my selected compression method?

     
  • Shell

    Shell - 2012-01-22

    Here are some actions you can take, the first is the most effective.
    1. Increase number of threads as much as many logical processors you have (the archive may become a bit larger).
    2. Decrease compression level (the archive will become much larger).
    3. Reduce the dictionary size (the archive will become larger).
    4. Reduce the word size (the archive will become somewhat larger)
    5. Do not use encryption.
    By the way, most of that is discussed in the help file.

     
  • Jay

    Jay - 2012-03-02

    So if I do this:

    1. Increase number of threads as much as many logical processors you have (the archive may become a bit larger).

    In conjunction with a normal-ultra compression level, then I should be finished compression my 1.86GB size folder less than a few hours? Not the 70hrs it would normally take the way I was doing it?

     
  • ZiNgA BuRgA

    ZiNgA BuRgA - 2012-03-04

    You can always start the compression and see what the ETA is.

    Other than 7-Zip settings, your actual CPU and RAM will have quite an impact on compression speed.
    As my AthlonX2 4200+ CPU wouldn't take anywhere near 70 hours to compress ~2GB files with one thread, my guess is that you have an older CPU (or you're running CPU intensive tasks, but I'm doubting that).
    7-Zip, by default, selects the number of threads based on your logical CPU count (up to 2 for LZMA), so if it's set to 1, then you probably only have a single core CPU.

    In which case, I would try u_shell's 2nd suggestion and reduce the compression level to something like 'Fast' or 'Fastest' and see how much that helps.  If you have a single core CPU, increasing threads won't make things faster.
    Also, seeing as you probably have an older computer, try reducing the dictionary size. 16MB dictionary consumes ~216MB of RAM, so if you only have, say, 256MB of RAM, and the OS and other programs are taking some memory, try reducing the dictionary size to something like 8MB.

     
  • dos386

    dos386 - 2012-03-04

    > In conjunction with a normal-ultra compression level, then I should be finished compression
    > my 1.86GB size folder less than a few hours?

    YES

    > Not the 70hrs it would normally take the way I was doing

    Possible reasons:

    - You have to wait until maybe cca 5% is compressed before ETA is useful (before it can be just garbage)
    - You have a genuine 80386 SX 10 MHz processor :-)
    - Your PC is wormed and the malware eats 99.9% of the performance of formerly your PC
    - Your dict setting is too big (should be <= 1/16 of your RAM)
    - Your "antivirus" blocks 7-ZIP falsely ASS'uming it to be a virus

     
  • dos386

    dos386 - 2012-03-04

    >  Compression Method

    keep Deflate for ZIP and LZMA for 7-ZIP

    > Dictionary Size

    see above

    > Word Size

    don't touch

    > Solid Block Size

    yeah

    > Number Of CPU threads

    don't care if you have just 1 CPU

    > Encryption Method

    don't care if you don't encrypt, otherwise keep default, use ZIP-Crypto for ZIP and AES-256 for 7-ZIP

     
  • dos386

    dos386 - 2012-03-04

    > You can always start the compression and see what the ETA is.

    see also my posts above and here: http://en.wikipedia.org/wiki/ETA

     

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