[Linux-HA] DBRD - split brain - and HA is happily migrating

[Dominik Klein]

Thomas Glanzmann wrote:
> Hello,
> I have drbd (newest version; same goes for heartbeat) running as a
> master/slave ressource on the latest heart beat ressource and had the
> following problem. I had a split brain situation 

In DRBD or in the entire cluster?

> and heartbeat made it
> possible to migrate from one node to another and I wonder how that is
> possible? How do other people handle this situation. My setup so far is
> the following:

You didnt give your drbd.conf, but I suppose you do not use DRBD 
resource fencing. Without resource fencing, it is perfectly possible to 
execute "drbdadm primary $resource" on a disconnected secondary.

Take a look at the resource fencing function in DRBD. The primary will 
then use another communication path to set the secondary resource to an 
"outdated" status. "drbdadm primary" on an outdated resource will not 
succeed unless you manually force it (the DRBD RA does not do that).

Read the "man drbd.conf" section about it and this link is also worth a 
read: 
http://blogs.linbit.com/florian/2007/10/01/an-underrated-cluster-admins-companion-dopd/

Regards
Dominik