[Pacemaker] How to properly define DRBD resources

[Nikita Staroverov]

>
> But it was causing trouble, trying to promote one of DRBDs and then 
> starting XEN. After it failed (because second DRBD was secondary) it 
> tried to stop both DRBDs and again. Also once it happened that XEN had 
> still device open and XEN was refusing to stop that VM.
>
> So a mess, stonith, and so on.
>
> Without pacemaker it works perfectly.
>
I haven't seen any colocation and order rules. So how should it work?