ReadyNAS Question Before Purchase

Rsync is a standard Linux backup protocol and is selected as the type of backup in the backup job.  It is unrelated to Resilio Sync.

Yes, it can make your head spin to sort through all the options and decide which is best when it's all new to you.  And I'm probably about to add to the pile.

ZeroTier can be used to join two networks into one virtual one (typical VPN use) but is more often (and by default) used as a "parallel" connection path.  As an example, my main NAS is 192.168.0.40 on my local network and 192.168.192.40 on ZeroTier (you choose the ZeroTier IP address at ZeroTier Central).  My backup is on my brother's network at 10.10 0.xx (I forget right now) and 192.168.192.45 on ZeroTier.  If put on my local network, 192.168.0.45 is reserved for it.  They use ZeroTier to talk to each other, but their local IP address to be accessed from PC's and to access the internet (for OS updates and such).

Like ReadyCloud, ZeroTier uses a "traffic cop" that's on the Internet, called ZeroTire Central.  Through it, you control what devices are allowed on your ZeroTier network  It just helps establish and control the connections, the data doesn't go through it.  So, I made an initial backup  with both NAS local, then gave it to my brother at Christmas time.  Though sending to the ZeroTier IP address, it was the same speed as if it were to a local one since it was physically on the local net  Once set up in his home, it just keeps updating the backups just as if it were still here (though slower, obviously).  I can also administer it remotely or directly upload or downlod from it with any device also running ZeroTier (One home PC, an Android phone, and my laptop) and enabled in my ZeroTier network.   I left space for him to use, and added a backup from the remote NAS to backup his important stuff.  I also only back up my most important things to the remote NAS.  Lesser items are backed up locally -- mine on another NAS and my brothers on a USB drive (which he prefers to be connected to his PC instead of the NAS, since administering the NAS is not in his wheelhouse).

If my brother wasn't using it for local storage, I'd probably have set the backup jobs as a "pull" from my main NAS to the backup NAS and put it on a power schedule, as I have done with the local backup.  One disadvantage of that, though, is that there is no log showing a "pull" backup took place and I've not enabled email notification.  It's only logged on the initiating system, so you can only get to it when power is on.  Locally, I can just turn it on if I want to check the logs, but it's not as easy when it's three states away.  I have not checked to see if ZeroTier supports WoL, which could help here.