[TUTORIAL] Creating a High Availability (HA) Shared Storage of a Two-Node DRBD-Based Cluster with RDMA-Based Networking

it seems there is no mention about the pve clustering - just setting up the drbd mirroring. so i have difficulties in understanding how this can work, as we need three nodes minimum with proxmox pve.
 
You use any 2 nodes (pve internal or external) for redundant storage representation and use all (or all others) pve nodes just as clients for vm/lxc images.