I investigated cloud storage options for off-site backup, but they would take months to “seed” over most normal internet connections, and those that allow you to mail in a seed hard drive are limited to 1TB. With each of my still shoots generating at least 4GB of data, until I’ve got a fiber connection cloud isn’t there yet. So I use the oldschool “sneaker net” method and backup to external drives which are then walked to a trusted friend’s house nearby. I back everything up as needed (usually weekly,) and this gives me a good reason to see my friend, as well!
For location gigs I use an assortment of small WD My Passport 2TB Portable External drives, two at minimum, one to back up the other, and then dump them onto the RAID when I get back home, at which time they enter the normal backup flow.