rsync on Mac OS X

[Giuliano Gavazzi]

Bruno, you do not say what version of MacOS X and what security  
update you have applied. This is important as there have been many  
changes in the last few versions, including a cockup with a security  
update that has been fixed with the latest one, although that should  
not apply with your options.

Also, you might have one of the volumes mounted with "Ignore Unix  
Permissions".
The best way to check this is:

  vsdbutil -h

note that usually you can check if that is set by doing a command-I  
on the volume to check, but this might not give you the answer in  
certain cases...

Giuliano