First of all, you’re going to need a VPN connection between your home and your office in order for any data to be transmitted between the two Drobo 5N2’s. Have you decided how you’re going to achieve that? One way would be to implement a VPN between the two firewalls, if they’re capable of doing so. It might also be possible to configure a VPN from the Drobo at home, but that’s beyond my ability to advise. I do not see any VPN configuration options within the Drobo Dashboard.
Once you have that part figured out, you could take advantage of DroboDR to back up your office data. This is a feature that is supported by the 5N2, and also the B810n. DroboDR automatically synchronizes data between the two devices: the source, and the target. For the purposes of your use case, the 5N2 at work would be the source, and the 5N2 at home would be the target. The one drawback to this approach is that the target – the 5N2 at home – gets dedicated to this task. You can still see and configure it using Drobo Dashboard, but you cannot write to it directly nor can you enable DroboApps.
That might not matter so much to you, if you weren’t going to use the 5N2 on your home network for anything other than synchronizing the data from work. Alternatively, if you were to create a VPN to work from your firewall, then you could always write data to the 5N2 at work from home, which would then be synchronized back to the 5N2 at home.