The problem with cloud-based solutions is that the cost for backing up several terabytes of data is typically several orders of magnitude higher than building your own RAID array, and the performance of Internet-based backup absolutely sucks beyond measure unless you're the sort of person whose data needs are measured in tens of megabytes.
- To back up 2 TB over a typical cable modem (say 3 megabit upload speed) will take you 61 days. Over typical DSL (300 kilobits per second), it will take almost two years.
- If you lose your original copy, getting the data back will be almost as painful. On a fairly fast cable modem (30 mbps), assuming the cloud-based backup server can completely saturate your downlink (which is by no means guaranteed), it will take you 6 days of continuous downloading to restore the backup. Over 3 megabit DSL, again, that number goes up to 60 days.
The ideal solution, if you can pull it off, would be to build a small concrete bunker in your yard, run power out to it, put a UPS and power conditioner in there to protect against bad power, put a RAID array in there, wire it with Ethernet to your house underground, put a watertight door on the thing, add a power cutoff that shuts down power if water does get inside (e.g. a GFI breaker and an unused extension cord whose output end is lower than your equipment), and hope for the best.
But more realistically, I would tend to suggest an IOSafe fireproof RAID array loaded up with five 6 TB drives (or maybe even 8 TB drives). Put it in a closet somewhere, and hope for the best. If you want to increase your protection a bit, you could also get two RAID expansion cabinets, store them at work, and periodically bring one home, clone your main RAID array to it, and bring it back