[Pacemaker] split brain in drbd dual primary setup

[Andrew Beekhof]

On Sun, Dec 6, 2009 at 8:31 PM, unni krishnan <unnikrishnan.a at gmail.com> wrote:
> Hi,
>
> We are using a cluster setup something like :
>
> http://picasaweb.google.com/lh/photo/e_uAYjG-8nh7oRZzXDp5HA?feat=directlink
>
> We are using
>
> OpenVZ for Virtualization
> DRBD with ocfs2 in dual primary mode
> heartbeat + pacemaker for HA
>
> Currently I have not added the drbd in pacemaker. But added the VPS as
> resources in pacemaker, so that the VPS can fail over or fail back.
>
> My question is, if I remove the cross over cable that connects the
> drbd then the two server will run in
>
> Primary/Unknown state and since the heartbeat connection which is
> through another cable is not broken, the VPS will run in two nodes.
>
> So the data written to two drdb devices in two nodes are different and
> it is not possible to discard data in any node. What is the better
> solution for this problem. Please give some hints, thanks :-)

In a word, fencing.
You need to configure a stonith resource and set the stonith-enabled
option to true.