[Pacemaker] Strange behaviour of dual master DRBD

[Michael Schwartzkopff]

Am Montag, 14. September 2009 14:27:40 schrieb Lars Ellenberg:
> On Mon, Sep 14, 2009 at 10:23:55AM +0200, Michael Schwartzkopff wrote:
> > Am Montag, 14. September 2009 09:51:45 schrieb Lars Ellenberg:
> > > On Fri, Sep 11, 2009 at 09:50:56AM +0200, Michael Schwartzkopff wrote:
> > > > Am Donnerstag, 10. September 2009 19:25:53 schrieb Lars Ellenberg:
> > > > > On Thu, Sep 10, 2009 at 05:10:39PM +0200, Michael Schwartzkopff 
wrote:
> > > > > > Hi,
> > > > > >
> > > > > > I configured a dual master DRBD-8.3.2. When the nodes stat there
> > > > > > is no problem. Both DRBD become master. But when I set on node to
> > > > > > standby and wake it up again, the DRBD on that node stays
> > > > > > secondary and does not become master.
> > > > > >
> > > > > > My config:
> > > > > > primitive resDRBD ocf:linbit:drbd params drbd_resource="r0"
> > > > > > ms msDRBD resDRBD meta notify="true" master-max="2"
> > > > > >
> > > > > > No further constraints.
> > > > > >
> > > > > > When the second node is online again ptest -sL shows:
> > > > > > (...)
> > > > > > resDRBD:0 promotion score on suse2: 50
> > > > > > resDRBD:1 promotion scpre on suse1: -1
> > > > > >
> > > > > > Since the "-1" prevents the resource from beein promoted, I
> > > > > > understand the behaviour of the cluster, but why isn't the
> > > > > > resource beeing allowed th become master on that node?
> > > > > >
> > > > > > Thanks for any enlightenting answers.
> > > > >
> > > > > Most likely it prevents you from shoting yourself in the foot ;)
> > > > >
> > > > > look at /proc/drbd and the kernel logs (appart from the ha.log, of
> > > > > course) on the drbd nodes to find out more.
> > > > > I bet you manoevered yourself into diverging data sets (aka DRBD
> > > > > "split brain").
> > > > >
> > > > > If it turns out to be a drbd.ocf bug,
> > > > > let me know.
> > > >
> > > > Hi,
> > > >
> > > > another confusing fact:
> > > >
> > > > The primitive DRBD was created without a monitor operation. When I
> > > > add a monitor operation, better two (Master,Slave) the described
> > > > problem goes away. But in my understanding the complete setup should
> > > > work as expected WITHOUT the monitoring operation.
> > >
> > > Well, your understanding is wrong.
> > > If you want the details,
> > > there is a lot of magic going on associated with the master scores,
> > > see the drbd.ocf script, drbd_update_master_score.
> > >
> > > You should definitely configure notify.
> > > You may get away without notify, if you configure monitor,
> > > and wait for a few monitor actions to happen.
> >
> > Hi,
> >
> > I configured the notification. My resource look like:
> > primitive resDRBD ocf:linbit:drbd \
> > 	params drbd_resource="r0"
> > ms msDRBD resDRBD \
> > 	meta resource-stickiness="100" notify="true" master-max="2"
> > clone-max="2" interleave="true"
> >
> > After putting one one to standby and online again I still get:
> > resDRBD:0 promotion score on suse1: 50
> > resDRBD:1 promotion score on suse2: -1
> >
> > So the resource will NOT get promoted. Only with monitoring this
> > behaviour disappears.
>
> Fine.
> So configure monitor.

Cool "solution" for the problem ;-)

-- 
Dr. Michael Schwartzkopff
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