BSR User's Guide - eng

BSR (Block Sync Replicator, hereafter BSR) is a high-performance data protection solution that synchronizes and replicates disk and volume devices at the block level in real time over the network. Beyond simple data mirroring, BSR captures every block-level change generated by the operating system and applies it consistently to a remote host, enabling continuous service availability, high availability (HA), and disaster recovery (DR) without downtime.

BSR was created by forking the existing Windows DRBD, which itself was derived from Linux DRBD(http://www.drbd.org), and rebuilding it as a cross-platform unified engine that supports both Windows and Linux with the same architecture and protocol. This provides a consistent replication model and management experience across heterogeneous operating systems, delivering a single, consolidated replication platform for multi-OS environments.

From an architectural perspective, BSR fundamentally resolves several limitations found in legacy DRBD implementations—such as inconsistencies with the Windows I/O stack, inefficient memory usage, lock contention issues, slow resynchronization under certain workloads, and performance degradation on large-scale volumes. As a result, BSR delivers improved stability and outstanding performance, even in high-bandwidth, high-IOPS, and large-capacity environments.

BSR provides an enterprise-grade block replication platform with the following capabilities:

  • Real-time synchronous and asynchronous replication with no impact on live I/O

  • High scalability supporting tens to hundreds of terabytes

  • Fast initial synchronization via filesystem-aware FastSync (Active Sector Transfer)

  • Enhanced stability for large-scale service and cluster environments

  • Unified protocols and management across both Windows and Linux

  • Highly reliable replication engine suitable for HA, DR, and multi-site deployments

In summary, BSR retains the key concepts and design philosophy of DRBD while evolving into a next-generation, cross-platform block replication engine, serving as a core infrastructure component for organizations requiring robust data protection, high availability, and remote-site disaster recovery.

 

bsr is distributed under the GPL v2 licence.

 

This user guide is organized as follows.

Overview Introduces the basics and key features of BSR replication.

Environment Describes the supported platforms and specifications. Before installing, you should refer to this content to check the required specifications and points to note.

Installation This section describes the installation process and precautions for Windows and Linux.

Configuration Describes various configuration methods and provides examples of configurations. You should know the basics of creating resources and what to look out for.

Working Describes the procedures and methods for actual operation. Among them, the basic procedures for operating resources and configuring them for efficient synchronisation are essential to understand.

Troubleshooting Describe the various failure situations encountered during operation and the procedures to deal with them. Covers disk failures, node failures, split-brain, and compatibility issues.

Optimization Describes how to optimise replication performance. Explains it in terms of throughput and latency.

Internals Describes in detail the internal workings of the BSR replication engine. If you want to understand BSR in more depth, we recommend reading this chapter.

Appendices Describes recent changes, configuration file formats, CLI commands, and more, and is updated with each bsr version revision.

 

BSR is an open source community (https://github.com/mantechnology/bsr, https://github.com/mantechnology/bsr/issues ) and anyone is free to contribute and participate in its development.

For questions regarding bsr, please contact Mantech at bsr@mantech.co.kr.