I'll do some additional testing to see if the results are affected by caching.
Not sure why you're surprised that I used .tar files for the compression testing. As I mentioned in the article, most of the time I'm creating bzipped tarballs from directories of files, so it made sense to use what is, for me, a common real-world use case. Your mention of tar.bz/.tbz makes me think there's some misunderstanding, since clearly I wouldn't want to test compression of already-compressed files. But perhaps it's I who am misunderstanding your suggestion. Please feel free to enlighten me. :)
Not sure why you're surprised that I used .tar files for the compression testing. As I mentioned in the article, most of the time I'm creating bzipped tarballs from directories of files, so it made sense to use what is, for me, a common real-world use case. Your mention of tar.bz/.tbz makes me think there's some misunderstanding, since clearly I wouldn't want to test compression of already-compressed files. But perhaps it's I who am misunderstanding your suggestion. Please feel free to enlighten me. :)