Backup to second Instance

Hello, dear TrueNas community,

I have had a Nextcloud and some websites running on a computer for a while. Now I have a new server and wanted to virtualize it with TrueNas. I moved the old servers into VMs.

So far, so good.

I now have 2 servers with TrueNAS-SCALE-23.10.2.
The 1st (server1) has the VM with Nextcloud and I have a 1TB SSD with an 880GB zvol that is integrated into the VM.

(There are more hard drives here, but the simplified representation should be enough).

The 2nd server (server2) has a 4TB SSD and is supposed to do the backups.

Now I’m wondering how I can back up the files from server1 to server2.

I’ve already read thousands of posts, but I haven’t come to any conclusion.

First I tried replication. The problem here is that snapshots must first be created on server1 and then transferred to server2. There is no free space on the hard drives of server1, however, as everything is taken up by the zvol. Then I found an option there called “Full Filesystem Replication” and I thought that this would copy all the datasets and zvols. But that is not the case, because the error message appears: “ERROR Dataset ‘S1’ does not have any matching snapshots to replicate.”

Then I thought I’d try Rsync and then create the snapshots on server2. I configured ssh there, set up Rsync, etc. This task works, but no zvols are copied. There are still around 5GB of files in the dataset, which are copied. Nothing more.

Does anyone have any ideas what else I could try?

Thank you very much.