It's only possible if you have access to your DNS or DNS configuration files. If you are locked behind a weak-o registrar, and a cPanel reseller or shared, you can't do it.
Actually, that's exactly why subdomains were invented. They were supposed to be different servers. www was to be a web server, mail.domain was to be a mail server, ftp.domain was supposed to be for FTP, etc. This was all done back when most servers couldn't handle the software, traffic, or multitasking of different things being done on the same computer.