Rick bought a Drobo 2, and it's a bit flakier than his gen 1 Drobo. If it gets jostled, it has to reboot and rebuild. He's concerned that it's a single point of failure and he'll lose his data. Leo says that Drobos are a RAID (called Beyond Raid) where if one drive fails, it rebuilds form the other drives. So it's not really a single point of failure. But if all the drives go bad, then he's in a world of hurt.
This is why Leo recommends having more than one backup, with one off-site. Leo also has a secondary NAS, which is Synology. He's a big fan of them. And he can use different drive sizes. Rick should check out their RAID calculator here (synology.com).
Synology is the way to go.