Proxmox ships a tool that verify if everything is right for the update (eg: pve8to9), and the wiki documentation is extensive and kept up to date. At work we s

Proxmox ships a tool that verify if everything is right for the update (eg: pve8to9), and the wiki documentation is extensive and kept up to date. At work we started with 6.x a few years ago, upgraded to 7.x a bit after releases, then same with 8.x without issue. We'll wait a reasonable while before upgrading to 9.x but I don't expect any issue. Note : same with integrated ceph update, did Reef to Squeed a few weeks ago, no issue.