13.3. Creating a DRBD resource suitable to act as a Xen VBD

Configuring a DRBD resource that is to be used as a Virtual Block Device for Xen is fairly straightforward — in essence, the typical configuration matches that of a DRBD resource being used for any other purpose. However, if you want to enable live migration for your guest instance, you need to enable dual-primary modefor this resource:

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

Enabling dual-primary mode is necessary because Xen, before initiating live migration, checks for write access on all VBDs a resource is configured to use on both the source and the destination host for the migration.