rsync with multiple threads

Hi there I need to transfer 200+ TB data from one storage server (Red Hat Linux based) to another (FreeBSD). I am planning to use rsync with multiple threads in a script. There are a number of suggestions on the Internet (find + xargs + rsync), but none of them worked well so far. I also need a reliable way to check whether all files/directories from the source server have been copied to the destination server. Any suggestions/help would be appreciated. Regards Bill