This article intends to introduce to you the deployment of a MySQL active passive high availability setup using DRBD. DRBD defers from the standard MySQL master-slave replication in a few ways:

1. DRBD replicates the data at the block device level where as MySQL replication does it work at the SQL query level. As such, DRBD manages to provide better performance and reliability for MySQL replication.
2. DRBD provides automatic and transparent fail-over in the event the master node fails. DRBD achieves this using a network heart-beat where the whole fail-over process is totally transparent to the applications accessing the MySQL.

The service, including its IP address, can be migrated to the other node at any time, either due to a failure of the active node or as an administrative action. The lower part of the illustration shows a degraded cluster. In HA speak the migration of a service is called failover, the reverse process is called failback and when the migration is triggered by an administrator it is called switchover.