I've got some external hard drives that I rotate in and store off-site but still nearby (down the street) for some data. I also have constant online backups running to various locations/services (Linode, AWS, CrashPlan, Dreamhost, some private services). I don't backup everything, only the irreplacable personal data (so, I'm not backing up Wikipedia dumps); at current count, at most 6TiB of the data is irreplacable.