i have tried to make a snapshot with the following command-line:
rsync -lHrtDpvP --link-dest=daten/ daten/ snap1/
but some files are copied instad of making hardlinks to the files and i don't know why!
the link-dest-dir is the same as the source dir, so it gives no difference between the source file and the link-dest-file!
why does rsync then copy some files and don't make hardlinks to it ???
The link-dest dir in your command is NOT the same as the source dir, it is a subdir of the destination dir (which presumably doesn't exist). You probably meant to use --link-dest=../daten (or an absolute path to the source dir).
See the man page for how the link-dest dir is relative to the destination path unless absolute.