Deep Dive: How Proxmox Actually Keeps Your Cluster in Sync (Corosync & pmxcfs Internals)

⚠️ Fair warning: I'm still learning this stuff, so some details might not be 100% perfect. Take it as a fellow homelab explorer's notes, not official docs! In my last post, we talked about the outside view of a Proxmox cluster — quorum, split-brain, and how Corosync's strict timeouts decide when a node is declared dead. We looked at token-passing and fencing from a bird's eye view. This time, let's crack open the hood and look inside . Proxmox VE's cluster features are incredibly powerful, but for a lot of us, it feels like a black box. How does it actually stay in sync? What happens byte-by-byte when you change a VM config? I went down a research rabbit hole diving into the source code of Corosync and pmxcfs , and here's what I found. 🏗️ Architecture Overview: Two Key Components Everything in a Proxmox cluster boils down to two layers working in tight coordination: 📝 Note: This diagram is reused from my original Japanese article on Qiita — too lazy to redraw it in English, sorry! The