Advanced FTP and Disk Cataloguer (AFD) is powerfull and easy to use tool. With AFD you can simply Define on what disk (FTP server) there is a necessary file.

Copy / Move / Delete files and folders from several disks.
To check for new, deleted, changed files on disks and FTP servers.
To find duplicates of files on disks and FTP servers
To exchange your collection with friends (Even if they do not have AFD, you may Compile your database into executable file, compiled databases are only 20-30Kb bigger then usual.)