DRBD

DRBD, which stands for Distributed Replicated Block Device, is a software-based solution for data replication in Linux systems. It creates a replicated block device that is synchronized between multiple servers. Essentially, DRBD mirrors a storage device (like a hard disk or partition) from one machine to another over a network connection. This replication happens at the block level, meaning DRBD intercepts all write operations to the local device and forwards them to its remote counterpart.

The primary use case for DRBD is to provide high availability for services and applications. By having an identical copy of the data on a secondary server, the system can failover to the replicated device if the primary server becomes unavailable. This ensures minimal downtime for critical applications. DRBD supports various replication modes, including synchronous and asynchronous, allowing administrators to balance consistency requirements with performance needs.

DRBD can be configured in several network topologies, such as primary/secondary, or multi-primary (though multi-primary requires careful consideration and specific DRBD versions). It works by creating a new virtual block device that can be treated like any other physical device, allowing it to be partitioned, formatted with a filesystem, and mounted. This makes it a flexible and powerful tool for building resilient storage solutions in Linux environments. It is often used in conjunction with clustering software to automate failover processes.