Fat Pipes
Is point to point connectivity setup where you can order bandwidth on demand? I ask because, once your archival data is in the cloud, how do you get it out? If you upload 50TB of data to Nearline, is it really cheaper to pay IronMountain for the upload, Google for uploads and monthly fees, AND keep your own 10gbps connection around on the off chance you'll need to download your archival data eventually, as opposed to running your own onsite archival system?
Otherwise, will you be paying IronMountain to download your data over THEIR fat pipe, onto LTO, and then mail that tape to you?
This is a problem in general with archival storage. You don't plan to need to retrieve it, but what happens when you do? I can't imagine your average company has that much extra bandwidth at any given point.