DRBD refers to block devices designed as a building block to form high availability (HA) clusters.Also possible to combine multiple devices driver for Linux(MD) and the network block device(NBD) to achieve similar functionality.
DRBD is done by mirroring a whole block device via an assigned network. DRBD can be understood as network based raid-1. Only two nodes are supported in 8.4.x. For the drbd9(dev in RC phase), multiple nodes can be supported as well. Diving into it and do hacks.
This project is one of its kind!