Comment 100 for bug 1185756

I had the same problem and found out that there is a different behaviour of the drbd agent between just stop and start the drbd resource or rebooting the system. When you stop drbd, the drbd module stay loaded so when you start drbd again, the validity check of the agent correctly detects an 8.3 module. However when you reboot, no module is loaded yet so the validity check thinks we have an 8.4 module. Then the agent loads the module but does not check the validity any more. So it uses the 8.4 tools to create the drbd devices. This fails! Adding a call to the validity check function just after the module is loaded fixes this problem. So no need to revert.

I just found this by trial and error so it could have side effects. Maybe Stefan can confirm that this is really fixing something.