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I want to reinstall my OS, but I don't have the hard drive space to backup any more (I have a RAID 1 array, so I haven't done it for a while). In my /home I have 284.8 GiB of data, and I have a spare 250 GB (or 217.4 GiB) hard drive that I've been using for backup.

What type of compression algorithm (if any) is capable of this type of compression? I don't care about the time, I have a quad core though, so something that utilizes all 4 cores would be great.

I have tried 7zip with no success. Ran on one core for two days and failed because of lack of space.

Any ideas?

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up vote 5 down vote accepted

7zip is not that bad, if it was not able to compress your 280g of data down to 250g you have either used the wrong settings (ultra-mode?) or the data you want to compress is already compressed (lets say a bunch of drm-protected and legally owned media files :) ).

so, you could try several approaches:

  • find duplicates of data and throw it away
  • compress text files differently than already compressed files
  • split up the 280g of data to 200g and 80g and try to compress them separately
  • invest less than 100$ (the price per g drops rapidily for years) in a 1t disk and forget about all the effort
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+1 for the 1TB disk. Use it for a weekly full-system backup when you're done. – invert Apr 7 '10 at 11:03
actually the 1TB harddrive is ~$80USD – Malfist Apr 7 '10 at 11:33
A lot of it is video data. 215.7 GiB is video data. – Malfist Apr 7 '10 at 11:35
Video data may be already compressed - what sort of video format is it in? – Douglas Leeder Apr 7 '10 at 13:43
many different ones. Typically it's an avi file. – Malfist Apr 7 '10 at 15:11

The fact that it is video data is the proble. The video data is probably already compressed, so it won't be able to be compressed further. Best option is another disk. I would buy a 1 or 1.5 TB disk, install the new OS on it, then copy the data over. Use the old disk as a backup for the most important data.

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I want to keep the old disk because it's two hard drives in RAID 1 configuration. – Malfist Apr 7 '10 at 15:12
I actually managed to compress the video data, all the way to 98.88% of it's uncompressed size, which was just enough to get it on the other hard drive. I'm moving most everything else to a 4th hard drive. – Malfist Apr 8 '10 at 12:57

pbzip2 will let you use all the cores on your machine, and tarring up the files first may achieve a slightly better compression ratio than 7zip. From the pbzip2(1) man page:

tar cf myfile.tar.bz2 --use-compress-prog=pbzip2 dir_to_compress/
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sidenote: just choose "solid" as the type of the 7z archive and you achieve the same effect as with tar. – akira Apr 7 '10 at 5:19
wasn't good enough compression. – Malfist Apr 7 '10 at 11:40

Sounds like you are hosed as far as using your existing set up. I would pick up an external HDD or an old computer and some new HDDs and run Freenas.


Break your RAID array.

Install your OS on one disk.

Mount the other disk.

Move the data to the newly installed system disk.

Rebuild the array.

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