Yes, I have another server at a different address, it's not only for backup, but yes, the servers complement each other with the most important data. I don't bother keeping everything backed up, just the irreplaceable data.
Renting space on somebody elses computer (cloud backup) makes sense if you only have a small amount to back up, once you get beyond several TB it gets messy or expensive. I prefer to keep my data myself. Connection speed is also a primary concern for some.