A basic difference between regular backups and disaster recovery backups is that disaster recovery backups must be transported to a different site. The remoteness of the recovery site depends upon the type of disaster you are preparing for (in the case of a fire, the recovery site can be around the corner; in the case of an earthquake or flood, it should be many miles away). The fact that the backups must be taken to another site means that they must be on a portable media: tape.