back up for wpmu site

Hello: I need to updated my theme and when I read the very important message it stated that it is critical to back up all files and database. I was searching for a plugin to do this... but did not find one. Ultimately this plugin would back up all of the sites so I never have issues with lost files and databases for subscribers as well.

PS I had to select a plugin to submit this question, so wordpress user synchronization is not applicable.

Thanks so much!