This guide describes DRBD version 8.4 and above. For 8.3 please look here.


6.8. Enabling dual-primary mode

Dual-primary mode allows a resource to assume the primary role simultaneously on both nodes. Doing so is possible on either a permanent or a temporary basis.

[Note]Note

Dual-primary mode requires that the resource is configured to replicate synchronously (protocol C).

6.8.1. Permanent dual-primary mode

To enable dual-primary mode, set the allow-two-primaries option to yes in the net section of your resource configuration:

resource <resource>
  net {
    protocol C;
    allow-two-primaries yes;
  }
  ...
}

After that, do not forget to synchronize the configuration between nodes. Run drbdadm adjust <resource> on both nodes.

You can now change both nodes to role primary at the same time with drbdadm primary <resource>.

6.8.2. Temporary dual-primary mode

To temporarily enable dual-primary mode for a resource normally running in a single-primary configuration, issue the following command:

# drbdadm net-options --protocol=C --allow-two-primaries <resource>

To end temporary dual-primary mode, run the same command as above but with --allow-two-primaries=no (and your desired replication protocol, if applicable).

6.8.3. Automating promotion on system startup

When a resource is configured to support dual-primary mode, it may also be desirable to automatically switch the resource into the primary role upon system (or DRBD) startup.

resource <resource>
  startup {
    become-primary-on both;
  }
  ...
}

The /etc/init.d/drbd system init script parses this option on startup and promotes resources accordingly.

[Note]Note

The become-primary-on approach is not required, nor recommended, in Pacemaker-managed DRBD configurations. In Pacemaker configuration, resource promotion and demotion should always be handled by the cluster manager.


This guide describes DRBD version 8.4 and above. For 8.3 please look here.