"10g for 2pB is 18 days of transfer - which sounds like a lot - but that's 5 days of transfer on each site, 1 day of setup, and 1 week of shipping."

I can confirm this, to some degree.

We have larger customers with 20 or 40 or 80 TB of data to bring into rsync.net and everyone is always very interested in physical delivery, which we offer, but it's always easier to nurse along a 20-30 day transfer than ship JBODs around.

As long as you have a transfer mechanism that can be resumed efficiently (such as zfs send) and you don't have terribly bad bandwidth, we always counsel to just run the very long transfer. It does help that we are inside he.net in one location and two hops away from their core in two other locations and we can just order 10gb circuits on a days notice ... because he.net rocks.