FreePBX High Availability with DRBD: Architecture and Storage Replication
by Provider Adminlast verified 2026-08-13
Overview
This guide details how DRBD (Distributed Replicated Block Device) powers block-level storage replication in FreePBX High Availability deployments. Readers will explore the architectural foundation of network-based RAID-1, synchronous replication protocols, and integration with cluster resource managers like Pacemaker and Corosync. Mastering DRBD mechanics ensures robust VoIP service failover, data integrity across database instances, and reliable state maintenance for critical telemetry.
Key takeaways
- DRBD operates as a network RAID-1, mirroring underlying block storage between active and standby FreePBX nodes.
- Synchronous replication (Protocol C) ensures that MySQL transactions, CDRs, and voicemail files are guaranteed on disk prior to operation completion.
- Pacemaker and Corosync orchestrate the DRBD resource states alongside virtual IPs, Asterisk, and database daemons.
- Network fencing and automated split-brain handlers prevent data divergence during node isolation.
- Proper MTU configuration and dedicated sync interfaces are essential to avoid media artifacts and database write latency.
Prerequisites
- Root access to two Linux systems running FreePBX in an HA cluster topology.
- Understanding of Linux Storage Stack components including LVM, filesystem creation, and block devices.
- Basic knowledge of cluster management concepts such as floating virtual IPs and split-brain conditions.
- Dedicated secondary network interfaces for high-throughput cluster cross-connects.
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