Clone two identical EX4100 and HDD's and then synchronise via remote backup

I have:
EX4100 (4GB RAM) and 4 6TB Red HDD’s, RAID10. This one is working already for a year or two. Have around 4 TB of data on it.

I thought:
Raid is nice but if the building burns out, my Data is lost too. So I bought another EX4100 (2GB RAM) and 4 gTB Red HDD’s, RAID10. The new NAS is at my home.

My problem:
Was not able to setup the remote backup. Was looking for videos and instructions. I think, I’ve done everything as described, but I still cannot select the destination folder.
Followed all the instructions, set on both the:
NAS passwords, SSH, remoteserver enabled, Port for SSH and Remote Backups.

STILL, the error basically says this:
Remote backup not possible due to unknown SSH-Host.
Remote backup cannot continue due to error with RSYNC-Test.

I wrote to the support but haven’t got any reply. Yet. Perhaps this will be solved soon.

Now, I was thinking:
Why not take out the [empty] HDD 2 and 4 from the new EX4100 and replace it with the [full] HDDs 2 and 4 from the old EX4100. Theoretically the automatic rebuild would kick in.

The question:
How do [both] devices know which HDDs should be rebuild? I mean I want to avoid that the [empty] HDD takes over and rebuild’s the [full] into [empty].

The thought:
OK, even if the old EX4100 would perhaps know that the HDD 2 and 4 is missing and that the “new” HDD 2 and 4 are used but empty, let’s make the [empty] a [full].

But, how about the new EX4100? Would this one also know that the HDD 2 and 4 from the old EX4100 are now the [full] and it would then make the HDD 1 and 3 from [empty] to [full]?

I hope my description and questions are clear.
Thanks to everyone reading and trying to help.
Not an expert here.


You could refer to the following link: