Proxmox uses quorum to determine which node the VMs will be automatically transferred to if a node goes down unexpectedly. If you have at least 3 physical servers in a cluster, you can set up high availability between the three servers. You will also need a NAS or some type of shared storage for this to work correctly.
Table of contents
Creating a 3 node cluster in ProxmoxHigh Availability with a 3 node clusterRemoving a node from a Cluster14 Impressions