Salut,
comme je n'ai rien trouve ici sur ce fameux logiciel je me suis dit que j'allais partager mon experience avec OSA 
Alors lrzip de ce cher Con Kolivas, est base sur rzip.
Les 2 pages qui expliquent de quoi on parle:
-rzip: http://rzip.samba.org/
-lrzip: http://ck.kolivas.org/apps/lrzip/README
En gros, on compresse avec un dictionnaire plus gros que bz2 et gz, ca prend (bien) plus de ressources mais ca compresse pas mal mieux.
Citation :
rzip is a compression program, similar in functionality to gzip or bzip2, but able to take advantage long distance redundencies in files, which can sometimes allow rzip to produce much better compression ratios than other programs.
Advantages
The principal advantage of rzip is that it has an effective history buffer of 900 Mbyte. This means it can find matching pieces of the input file over huge distances compared to other commonly used compression programs. The gzip program by comparison uses a history buffer of 32 kbyte and bzip2 uses a history buffer of 900 kbyte. The second advantage of rzip over bzip2 is that it is usually faster. This may seem surprising at first given that rzip uses the bzip2 library as a backend (for handling the short-range compression), but it makes sense when you realise that rzip has usually reduced the data a fair bit before handing it to bzip2, so bzip2 has to do less work.
Disadvantages
rzip is not for everyone! The two biggest disadvantages are that you can't pipeline rzip (so it can't read from standard input or write to standard output), and that it uses lots of memory. A typical compression run on a large file might use a couple of hundred MB of ram. If you have ram to burn and want the best possible compression rate then rzip is probably for you, otherwise stick with bzip2 or gzip.
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Citation :
Long Range ZIP or Lzma RZIP
This is a compression program optimised for large files. The larger the file
and the more memory you have, the better the compression advantage this will
provide, especially once the files are larger than 100MB. The advantage can
be chosen to be either size (much smaller than bzip2) or speed (much faster
than bzip2). Decompression is always much faster than bzip2.
Lrzip uses an extended version of rzip which does a first pass long distance
redundancy reduction. The lrzip modifications make it scale according to
memory size.
The data is then either:
1. Compressed by lzma (default) which gives excellent compression
at approximately half the speed of bzip2 compression
2. Compressed by lzo which on most machines compresses faster than disk
writing making it as fast (or even faster) than simply copying a large file
3. Leaving it uncompressed and rzip prepared. This form improves substantially
any compression performed on the resulting file in both size and speed (due to
the nature of rzip preparation merging similar compressible blocks of data and
creating a smaller file).
4. Compressed by bzip2 as an rzip-like compression format.
The major disadvantages are:
1. It only works on single files. To get the best performance out of the
compression it is best to tarball all your files together.
2. It requires a lot of memory to get the best performance out of, and is not
really usable (for compression) with less than 256MB. Decompression requires
very little ram and works on small ram machines.
3. Does not work on stdin/stdout.
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Test sur un repertoire de 2 fois le meme mp3 avec juste 2 noms differents (j'ai pris justement un cas ou generalement un tar suffirait vu que le mp3 est deja compresse):
- mp3: 50Mo
- repertoire: 100Mo,
- tar du repertoire: 99Mo,
- tar.bz2 du mp3: 47Mo
- tar.bz2 du repertoire: 93 Mo,
- lrzip -M du mp3: 45Mo
- lrzip -M (LZMA) du tar (lrzip ne fonctionne que sur un fichier et pas sur un repertoire): 45Mo
- lrzip -b (bzip2) du tar: 45Mo
Les resultats parlent d'eux memes, lrzip se rend compte que j'ai les donnees en double, bz2 non.
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"Phildar t'es vraiment une pute pas finie toi! Et Manu le gros porc arrete de t'marrer!"
