You want to run a periodic MySQL Backup for your site.
A MySQL Backup is a simple thing to do when the amount of data isn't too much. Unfortunately it almost always is.
Most of the MySQL backup techniques require you to have root access to the MySQL server or shell rights on the hosting server. Which is seldom the case.
Other solutions are web-based and can't handle large quantities of data, scripts will time out and the information won't be handy.
Most of them won't allow you to restore the information with the same ease and the Internet is filled with people asking why can't PhpMyAdmin import lots of Megs of sql. The solutions are awkward at best.
SiteVault will give you the possibility to backup and restore as much sql data as your hard-drive or the hosting company allows.