Pacemaker DRBD resource not getting promoted to master on any node

Make sure that your DRBD device is healthy. If you # cat /proc/drbd and look at it's state, do you see the following: cs:Connected, ro:Secondary/Secondary, and most importantly, ds:UpToDate/UpToDate?

Without UpToDate data, the resource agent for DRBD will NOT promote a device. If you've just created the device's metadata, and haven't forced a single node into the Primary role yet, you'll see your disk state is: ds:Inconsistent/Inconsistent. You'll need to run the following to tell DRBD which node should become the SyncSource for the cluster: # drbdadm primary r0 --force

That's the only time you should have to force DRBD into Primary under normal circumstances; so forget the --force flag after that ;)