When my computer died before (through no fault of my own) I promised myself that I'd use that for the impetus to start keeping backups. I haven't done it yet, and the night before last I dreamed that my computer died because of the massive blackout we had, and I even chided myself in my dream for not doing what I said I'd do with backups.
So last night I left my computer backing up all night... I wanted to see how much I could expect my data to compress so I could see how much work I had to do to make it fit on a CD-RW. I had wanted to use tar.bzip2, but for whatever reason 7-zip's bzip support is broken, and I was too lazy to download the executables for tar and bzip and learn their command line arguments. I had decided I wanted a format which worked like tar.gz where it concatenates all your files together and then compresses them, so I tried out 7zip's own format since it can create "solid archives" which do just that.
It took a little over 2:15 to compress my whole 1.9 gigs of data in my c:\keith folder ("My Documents") onto a different drive (which probably significantly sped it up compared to what it would have been had I compressed it onto the same drive), and using 7-zip it compressed down to 731 megs.
I woke up during the night after it had finished, so I decided to see what that would have been with zip compression. Obviously it's not a fair comparison because zip doesn't group the files together before compressing, but I wanted to see how much of a difference it made. Plus, since I was going back to sleep, it took essentially no time 
7-zip's zip compression compressed it down to 1.19 gigs in a little over 1:15.
For reference, I'm using a 700 mhz computer with 384 megs of RAM backing up from a 7200 RPM 20 gig drive to a 5400 RPM 40 gig drive.
Now I have to try out tar.gz and tar.bzip2 to see how much of a difference there is. I'd obviously rather use more standard formats (rather than 7-zip) for backup.
Saturday, August 16, 2003
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Let us know how this goes, I'd be interested to hear.