MrC Wrote: > Have you actually tried binary data diffs with large files? > ... > And the storage required is almost as large and sometimes larger than > the file itself. > Have *you*?
I have never used rdiff-backup, but I have used xdelta. Here is a simple non-scientific benchmark, although still fairly representative of the kind of diffs that would be generated in this application. This is using xdelta, which I believe to be pretty good at generating binary diffs. % metaflac --list --block-type=VORBIS_COMMENT test1.flac METADATA block #2 type: 4 (VORBIS_COMMENT) is last: false length: 300 vendor string: reference libFLAC 1.1.0 20030126 comments: 10 comment[0]: ALBUM=Dark Side Of The Moon comment[1]: ARTIST=Pink Floyd comment[2]: DESCRIPTION= comment[3]: GENRE=Pop/Rock comment[4]: TITLE=Us And Them comment[5]: TRACKNUMBER=6 comment[6]: replaygain_track_gain=-2.13 dB comment[7]: replaygain_track_peak=0.696075 comment[8]: replaygain_album_gain=-3.67 dB comment[9]: replaygain_album_peak=0.968200 % metaflac --list --block-type=VORBIS_COMMENT test2.flac METADATA block #2 type: 4 (VORBIS_COMMENT) is last: false length: 262 vendor string: reference libFLAC 1.1.0 20030126 comments: 6 comment[0]: ALBUM=DskjdfhskjfhOf The Moon comment[1]: ARTIST=Pink Floydslsekjlwerjkwlkj comment[2]: DESCRIPTION=lkasjdfajfowierskdjflskjflasd lkjdfsklfj sdfkslkdfjasldfjalkdf comment[3]: GENRE=aksjdfaslkdjfla comment[4]: TITLE=lskdjlaskdfjsaldkfj comment[5]: TRACKNUMBER=87 % xdelta delta test1.flac test2.flac diff % ls -l 413 2005-11-12 10:18 diff 45651843 2005-11-12 10:11 test1.flac 45651843 2005-11-12 10:16 test2.flac > This would take ages for larger libraries! Clearly binary diffs can be very efficient indeed. This took about 5 seconds, would probably be 20 if they weren't cached. So, yes, it would be a long time for a large library, but it would be no worse than rsync. (In practice, you could selectively ignore files based on the last-modified time and filesize) -- clumsyoik ------------------------------------------------------------------------ clumsyoik's Profile: http://forums.slimdevices.com/member.php?userid=1997 View this thread: http://forums.slimdevices.com/showthread.php?t=18029 _______________________________________________ Discuss mailing list Discuss@lists.slimdevices.com http://lists.slimdevices.com/lists/listinfo/discuss
