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Offline Snake X

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best compression method?
« on: June 24, 2011, 12:02:37 pm »
I have about 170 GB of storage (or will get there shortly), and i need to move that stuff over to a 150 GB raid setup (only way to do it). Now, with that said I need to chop off about 20 GB, and what is the **BEST** compression method that I can do to achieve this? I do NOT care how long it takes to compress, i just need to do it.

rar?
7z?
tar?

which one, or something else?

thanks!  :thumbsup:
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Offline Munchor

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Re: best compression method?
« Reply #1 on: June 24, 2011, 12:04:56 pm »
7zip is the best one if you want smaller size. However, zip is the fastest one to compile, but I see you're interested in 7z here.
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Offline Snake X

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Re: best compression method?
« Reply #2 on: June 24, 2011, 12:06:28 pm »
someone told me tar was the best of them all though... :???
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Offline Munchor

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Re: best compression method?
« Reply #3 on: June 24, 2011, 12:08:52 pm »
http://ubuntuguru.wordpress.com/2007/03/09/whats-the-best-file-compression-method/

Well, at least tar.gz and tar.bz2 are missing there, but from all those 7z is the faster.
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Offline Snake X

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Re: best compression method?
« Reply #4 on: June 24, 2011, 12:14:40 pm »
ok so in 7z, what is the best compression method that I should use?
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Offline Munchor

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Re: best compression method?
« Reply #5 on: June 24, 2011, 12:15:13 pm »
Quote from: Snake X on June 24, 2011, 12:14:40 pm
ok so in 7z, what is the best compression method that I should use?

The extension *is* called .7z
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Offline Snake X

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Re: best compression method?
« Reply #6 on: June 24, 2011, 12:19:40 pm »
i mean as in:

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Re: best compression method?
« Reply #7 on: June 24, 2011, 12:30:04 pm »
Sorry, but my Archive Manager doesn't ask for any of that. Try the 4 of them with a 100MB Folder and see which one gives better results. But I don't think it matters so much, go with default.
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Offline AngelFish

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Re: best compression method?
« Reply #8 on: June 24, 2011, 12:47:02 pm »
If you're going to use 7zip, use PPMd. However, if you'd like something with even higher compression, try PAQ, which is generally considered one of the best general purpose compression algorithms in existence.

That said, what algorithm you use depends heavily on what you're compressing. If you're compressing things with a lot of repetitive data, simple Huffman encoding will give you a near optimal results. If you're compressing random binary noise, no compression algorithm is going to do well.
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Offline alberthrocks

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Re: best compression method?
« Reply #9 on: June 24, 2011, 01:05:56 pm »
To correct, tar is NOT a compression method. It's just a nice format to combine directories and files into one file, and then a compression (like BZIP, GZIP, etc.) is applied onto that file.
To explain visually:

Code: [Select]
[ Files and folders! ]       [ TAR Archive    ]       [ bzip2 Compress ]
[ somefolder/        ]       [                ]       [                ]
[    file1           ]       [ DATA           ]       [ data compresed ]
[    file2           ]       [                ]       [ with RLE, BWT, ]
[    file3           ]       [ somefolder blk ]       [ MTF, RLE, then ]
[ somefolder2/       ]  ==>  [   file1 blk    ] ==>   [ Huffman, base  ]
[    afile1          ]       [   file2 blk    ]       [ 1, delta enc., ]
[    afile2          ]       [   file3 blk    ]       [ bit array!     ]
[    afile3          ]       [ somefolder2 blk]       [                ]
[ anotherfile1       ]       [   afile1 blk   ]       [ TAR ARCHIVE    ]
[ anotherfile2       ]       [   afile2 blk   ]       [     ↓↓↓        ]
[ anotherfile3       ]       [   ...          ]       [ BZip2 comp. dat]

blk = data block entry for file/folder/link
More info about tar and compression (bzip2) can be found here:
http://en.wikipedia.org/wiki/Bzip2
http://en.wikipedia.org/wiki/Tar_%28file_format%29

Hope this helps! :)
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