How To Compress Large Files With 7-zip
Carey Jangam
7-Zip is a free and open-source file archiver for compressing and uncompressing files. If you need to save some disk space or make your files more portable, this software can compress your files into an archive with a .7z extension.
Launching your website is easier than you think. With up to $2,493 in web hosting savings, bringing your business online is easier and more affordable than ever. Act now to take advantage of this limited time offer.
Hi, I saw in a tutorial in youtube how to compress file using 7zip. One example shown was a 4gb file compressed to 800 mb . I tried it on my end to compress a 1.37 gb file and I was expecting it to be smaller in size but I got the same file size as the original. Why is it like that?
This article does not cover splitting up large files. We do not yet have a guide for that, but I did find a tutorial for you that goes over how to do this. Check out How to split large files with 7zip and see if that helps you. We have not tested the guide, nor do we endorse the site, it was just something I found when searching the web.
I have downloaded the 7 zip folder but it seems i cant get to the add botton. I am using windows 7 with 64 bit operating system but it just cant work! When you open the folder, only you see as icons are the following: organize, include in library, share with etc.
The amount of compression will vary depending on the file and its type. For example, text files (htmp. php,etc) can usually compress somewhat. Some files such as image and pdf files do not compress much at all. As for the types of compression available in 7-zip, I tested a txt file with each type. The top 4 compression formats, starting from the smallest, are .xz, .7z, .gz, and .zip. The difference between each was very small, so all formats will be fine.
Some file formats cannot be further compressed. For example jpeg file are already compressed and will not zip much smaller. In this case you can optimize the images by size, meta tags, etc. Which reduces the file sizes.
7-Zip is by far now the most popular compression and decompression tool. A large part of this popularity is because 7-Zip supports decompressing so many formats. This is a great niche that 7-Zip has created for itself.
However in the area of very large files 100 GB+ etc and streaming compression 7-Zip is often not the fastest/best tool to use. 7-Zip barely achieves 10-15 MB/s on LZMA at the fastest setting on common Core i5 and similar machines. When transferring disk images over the network today's 1 Gbps connections are barely maxed out by 7-Zip. Further disk random I/O speeds have also moved beyond 30 MB/s. So even if one is reading and writing compressed data to the same disk, the process becomes CPU bound and usually never I/O bound or RAM bound.
TCP/IP like exponential backoff. Assuming LZMA compressed data in 1MB chunks. If the compression ratio is poor i.e. say compressed data size is not less than 90% of the uncompressed size, then skip compressing the next 1MB. Test the third chunk of 1MB. If this chunk is also not compressible then skip ahead 2MB. And define a max skip length of 4MB or 8MB. This will work very well for very different filetypes in a directory - some compressible, some not and system images. Especially it will work very usefully during backup operations with GBs of data.
Instead of exponential backoff one could grab some source from Testdisk/Photorec which has the ability to detect filetypes in a stream. One could skip compressing already compressed files like mp3, mov, mp4, zip etc. This will also make dealing with large data very fast and efficient.
I'm using the command line off the latest debian x64 live cd 7z version 9.2. i'm piping data from ntfsclone or dd. I'm using "7z -a -an -txz -mmt=4 -mx=1 -ma=0 -si -so -mhc=off". To test speed I'm just piping to /dev/null. The max throughput I can achieve is around 12MB/s. The machine is a core i5 2ghz laptop with 6 gb ram. Just piping ntfsclone or dd directly to /dev/null gives more than 40 MB/s. The only improvement I was able to get was by adding -md=1k which improved throughput to 14 MB/s. Tweaking other parameters like fb, mc etc didnt show any improvement.
4) Note that p7zip in linux sometimes can be compiled without speed optimization -O2 switch. So if you recompile it with -O2, you can get some improvement in speed.
You can compare the speed with 7-Zip for Windows.
You can run 7za.exe via WINE.
Its a real data file - the first 1 GB of a VMware Win 7 x64 installed virtual machine vmdk disk file on the hard disk. The compressed output is written to a ram disk, so that read and write to the same disk doesnt slow 7z down. While imaging a disk, the output is usually not to the same disk.
From what I understand of LZMA2 algorithm
1. Read chunk of data (for example 10 MB)
2. Compress using LZMA algorithm.
3. Check if compressed data size is less than original data size of 10 MB. If compressed data is smaller then write compressed data to output, else write original data to output.
My first suggestion (Only for fastest mode)
1. Read chunk of data (for example 10 MB). Initialize skip ahead counter to 1.
2. Compress using LZMA algorithm.
3. Check if compressed data size is less than original data size of 10 MB. If compressed data is smaller then write compressed data to output, else write original data to output.
4. Skip ahead check:
a) Skip ahead bytes = Skip ahead counter * Chunk size (10 MB = 1 * 10 MB = 10 MB
b) If compression ratio is more than 90% (compressed data size is greater than 90% of original data size) then skip compressing the next set of bytes upto size of skip ahead bytes (i.e. write the next skip ahead bytes of uncompressed data directly to output). Increment skip ahead counter else if compressed size is less than 90% of uncompressed data reset skip ahead counter to 1.
So as an example. Lets say there is 100 MB of data to be compressed. LZMA will compress the first 10 MB and check if the compressed data is less than original data. Lets assume the compressed data size is greater than 90% of the original data size. Then just copy the next 10 MB of data (10MB offset to 20MB) directly to output (Dont even compress and check). Then compress the third chunk (20-30 MB) and check. If third chunk compressed size is also more than 90% of original data size then skip ahead 20MB i.e. copy the next 20MB directly to output without any compression. Then check the next 10MB chunk (50MB offset to 60MB) and so on...
My second suggestion (Again only for fastest mode)
See this program PhotoRec (See the section on how PhotoRec works) It can detect various filetypes very fast in a data stream. See this _Formats_Recovered_By_PhotoRec
However, the ram usage rose to 8GB and stayed there!
For some reason, even after exiting 7Z, Windows Explorer grabs those 8GB of ram usage, and remains with them!
I've looked in task manager, and 7z successfully exited the memory.
Any idea why explorer all of a sudden uses the RAM that 7z used?
1. dictionary larger than total size of files compressed cannot improve the ratio
2. it mat be bad idea to use for 7z compression more than your RAM minus 500 mb or so. it may result in a LOT of swapping and operation may be performed as long as day or week
It seems 7z is building memory usage as the dictionary size gets larger, but for some reason the first time I tried it the memory usage immediately jumped to 8GB (from 1GB usage).
Any subsequent tests I did the memory starts basically from system memory and gradually builds up the file.
It seemed from tests that, when selecting the compression method by the memory usage for decompressing, that when setting this value much lower than the original file it's size, increases the file size of the output file (which is understandable). Setting it higher than the original file size also increases filesize, and makes little sense, as 7z seemingly reserves space for the larger dictionary, which is not optimally used.
Efficiently managing large files is essential for effective storage and sharing. This helpdesk article provides guidance on how to zip files using 7-Zip on Windows or alternatively, Keka on your Mac and (please note that there are other options available, and these are just examples, offered as freeware at the time of writing).
Splitting Files becomes necessary when zipped files exceed 50 GB in size, as 50 GB is the maximum file size that can be shared for importing directly using your Power Diary Account via Setup > Data Import.
To access and share the split zip segments on Mac, simply double-click on the first segment (e.g., filename.zip.001). Keka will automatically detect the other segments and combine them to extract the original files.
By following these steps on both Windows and Mac, you can effectively zip and, when necessary, split large files for efficient storage and sharing with us for import into your new Power Diary Account. This process ensures that even files exceeding 50 GB can be managed effectively.
You must run 7-Zip File Manager in administrator mode. Right-click the icon of 7-Zip File Manager, and then click Run as administrator.Then you can change file associations and some other options.
You can get big difference in compression ratio for different sorting methods,if dictionary size is smaller than total size of files.If there are similar files in different folders, the sorting "by type" can provide better compression ratio in some cases.
Note that sorting "by type" has some drawbacks.For example, NTFS volumes use sorting order "by name", so if an archive uses another sorting, then the speed of some operations for files with unusual order can fall on HDD devices (HDDs have low speed for "seek" operations).
If you have such archive, please don't call the 7-Zip developers about it.Instead try to find the program that was used to create the archive and inform the developers of that program that their software is not ZIP-compatible.
7fc3f7cf58