How to Build a High-Availability (HA) Cluster on Bare Metal
When deploying mission-critical applications, a Single Point of Failure (SPOF) is a disaster waiting to happen. High Availability (HA) is one of the key architectural requirements for achieving uptime targets such as 99.99%, provided that the surrounding infrastructure is also redundant. In this guide, we will architect a production-grade, 7-node High-Availability cluster from scratch using bare-metal servers connected via a Private VLAN. Phase 1: Architecture Explanation (Visualizing the Setup) Before touching the command line, you need a clear mental model of the topology. We are distributing our services across three isolated tiers: Floating IP (VIP): The single public IP address (203.0.113.100) that users hit. Tier 1 (Load Balancers): Running HAProxy and Keepalived in an Active/Passive setup. Tier 2 (Web Servers): Running Nginx and your application code. Tier 3 (Database Cluster): Running a MariaDB Galera Cluster for certification-based replication. IP Addressing Scheme H...