I tried to use Crashplan. I have a full-duplex 50 Mb/s fiber ISP link. Initially, upload speeds were in the 5 Mb/s region, but dropped lower and lower as time went by. After several months, my 6 TB backup was about a third done. The the desktop client program stopped working, and I never put much effort into getting it started again because the performance was so bad.
Crashplan used to offer to ship you a hard disk with your data for recovery, but they no longer do so. At the rates I saw -- assuming they applied to downloads -- it would take almost a year to recover 6 TB of data.
I'm back to carting spinning rust 8TB drives back and forth from the safe deposit box.