During the weekend, I had added another 250GB SATA drive to my server, so I could do more routine backups now. Hard drives are really inexpensive right now, a 250GB hard drive costs just above 100. This upgrade should get me going for quite a while.
Originally, I was planning to add an external hard drive to do the backup. To my surprise, the external ones cost at least twice as much as the internal ones (eventhough the drives these external hard drives use are exactly the same, and in most cases they are actually cheaper since most of the external hard drives still use the PATA harddrives). I guess if you really want to get an external drive, you would save a lot of money by getting an external drive enclosure and buy a bare drive separately.