Problem with ceph upgrade before proxmox upgrade

You are running ceph with two nodes? The '/etc/ceph/ceph.conf' (symlink) is present?
 
Yes, sorry for that, I forget to write it in my post. This cluster consist from two nodes.

To answer your question, no, there is not /etc/ceph/ceph.conf symlink. Maybe this is the problem? Where would symlink point to?
 
To answer your question, no, there is not /etc/ceph/ceph.conf symlink. Maybe this is the problem? Where would symlink point to?
I hope you don't mind me asking, but did you install and configure ceph? As, a manual installation would put the config file into the directory and through pveceph, the symlink would be created. With pveceph, the config file is under /etc/pve/.