You need a SysAdmin. Now, this SysAdmin can be you (really, knowing the basics of server janitoring helps you as a developer and as a web designer, and as the guy who makes hosting decisions. Learning at least the basics of Linux is a good career move for almost everyone) but if not, you need to find someone you can depend on.

The other option is to find a host that specializes in hosting drupal sites and is willing to take care of all that for you. The biggest problem with this is that you can only use the features they install for you. Of course, they will also charge more than generic hosting, but it's still cheaper than getting a SysAdmin.