looked into ZFS but if I use that it halves the available disk space to 2TB.

Look harder :-)

ZFS can do it either way.

I don’t get it. Maybe I’m dumb… but:

If I am used to work with command line tools, then what do I need this GUI for?

Shut down, check all the wires and plugs. So many times it is the simple things.

If it’s not hardware, then it’s the filesystem: Either some disk (or quota) is full, or not mounted, or a filesystem is damaged.

You should continue to wear your wizard’s hat with pride. 🧙‍♂️

Have a look at Proxmox.

I would never want anything else anymore as the base system on a server.

Now I would double check your name services.

First reboot the Fritz 7490, then the Fritz 4040.

Then ping from everywhere to your Pi AND also ping from the Pi to every other machine: all the names must resolve to the proper addresses.

bind [::1]:80: Permission denied channel_setup_fwd_listener_tcpip: cannot listen to port: 80 Could not request local forwarding

Some service is still grabbing your port 80, so the new job cannot start to listen there.

However i can not connect to port 80 for OMV

But this service is not really listening.

Maybe your first installation job is not 100% finished, but still ‘hanging around’ somehow?

Just a thought - I do not really know OMV.