Configuring DRBD

The Pacemaker based RabbitMQ server requires a DRBD resource from which it mounts the /var/lib/rabbitmq directory. In this example, the DRBD resource is simply named rabbitmq:

rabbitmq DRBD resource configuration (/etc/drbd.d/rabbitmq.res). 

resource rabbitmq {
  device    minor 1;
  disk      "/dev/data/rabbitmq";
  meta-disk internal;
  on node1 {
    address ipv4 10.0.42.100:7701;
  }
  on node2 {
    address ipv4 10.0.42.254:7701;
  }
}

This resource uses an underlying local disk (in DRBD terminology, a backing device) named /dev/data/rabbitmq on both cluster nodes, node1 and node2. Normally, this would be an LVM Logical Volume specifically set aside for this purpose. The DRBD meta-disk is internal, meaning DRBD-specific metadata is being stored at the end of the disk device itself. The device is configured to communicate between IPv4 addresses 10.0.42.100 and 10.0.42.254, using TCP port 7701. Once enabled, it will map to a local DRBD block device with the device minor number 1, that is, /dev/drbd1.

Enabling a DRBD resource is explained in detail in the DRBD User’s Guide. In brief, the proper sequence of commands is this:

drbdadm create-md rabbitmq  
drbdadm up rabbitmq  
drbdadm -- --force primary rabbitmq