Looks like we were doing the math at the same time (see my post elsewhere, here). You'd be looking at 15 of these servers, but then I have no idea how much the expense of maintaining them would be. That's also the cost of storing their current data plus redundancy. It may be the cheap solution, today, but I wonder if it would scale on the order of a seriously high end tape system (I linked one in this thread that potentially stores 91 archived petabytes).

I couldn't find pricing information and since this isn't something I ever deal with, I don't know what the industry standard would be. I would not be surprised if the cost of setting up a very high capacity tape system would come out as the better deal in the long run. Perhaps the BackBlaze solution would be cheaper with half to a full petabyte, but over the long term, the high capacity tape systems might beat the multi-petabyte pants off it.

Of course, that kind of depends on how quickly spinning drives expand in size and drop in price, which could feasibly account for the difference in cost between the two options over time. The important variable there is in whether their data accumulation outpaces the drop in prices on spinning drives.

No matter what, cloud hosted solutions seems pretty much off the charts. Even if the storage was reasonable, I'm guessing they have to transfer several terabytes a month to the backup which would be pretty painful on a lot of networks.