On 21.06.2010 10:53, Matthias Schniedermeyer wrote: > On 17.06.2010 15:37, super master wrote: > > Hello, > > many linux SW is starting to implement new lzma compresson instrad of old > > zlib (gzip) od bzip2. > > > > lzma is default comrpession in very good compression SW 7-zip, which is > > faster and have higher compression ratio then bzip2 or rar. > > > > Currently its probalby the best compressor in therms of compression and > > decompression speed / compression ratio. > > > > In linux there is GNU lzma SW which implements lzma algorithm. > > > > In my optinion it would be very useful if rsync could use this compressor > > optionaly as upgrade of old zlib. > > > > more info: > > http://en.wikipedia.org/wiki/Lempel%E2%80%93Ziv%E2%80%93Markov_chain_algorithm > > lzma draws most of it's strength from using a much larger "Working > Window" (megabyte to gigabyte, instead of a few kilobyte like gzip). > > AFAIU rsync works with blocks in the kilobyte-range, which effectivly > prevents lzma from using it's main strength. > > > For illustration i've just tried "xz -0" on a linux-kernel tar-ball. > "xz -0" still uses a much larger window that gzip! The man-page says > about 6 megabytes and the man-page reserves a future change to an > algorithm other than lzma. > > On said linux-kernel tar-ball the compression was only slightly better > that gzip. > > 87634801 byte for gzip with defaults > 86841598 byte for gzip -9 > 85544824 byte for xz -0 > > For comparison: > 55044372 byte for xz -e9
A little addendum. I have looked on the wrong table in the man-page. memory-usage vs. dictionary size. I used the first, while the other is the correct one. For "xz -0" the dictionary size of 64KiB is "only" twice the maximum dictionary size of deflate and not orders of magnitute larger than the "64MiB" for -9. Bis denn -- Real Programmers consider "what you see is what you get" to be just as bad a concept in Text Editors as it is in women. No, the Real Programmer wants a "you asked for it, you got it" text editor -- complicated, cryptic, powerful, unforgiving, dangerous. -- Please use reply-all for most replies to avoid omitting the mailing list. To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html
