[Pacemaker] Split-brain on DRBD + Corosync/Pacemaker

[Digimer]

Is fencing/stonith configured in pacemaker? Can you call a fence against
a peer in pacemaker and trigger a reboot of the target node? If that
doesn't work, then you don't have proper fencing in pacemaker and the
crm-fence-peer.sh hook script won't work.

So yes, you need stonith and you need to make sure it actually works.
Look in Clusters From Scratch, I think it's around ch. 9. You need an
external method of powering off a node. This is generally done with
IPMI, iLO, RSA, DRAC or when those aren't available, a switched PDU like
the APC AP7900 (or your country's version of) will work.

On 12/19/2012 12:48 PM, Felipe Gutierrez wrote:
> Hi Digimer,
> 
> I am already using crm-fence-peer.sh
> 
> resource r8 {
> handlers {
>     fence-peer "/usr/lib/drbd/crm-fence-peer.sh";
>     after-resync-target "/usr/lib/drbd/crm-unfence-peer.sh";
>     split-brain "/usr/lib/drbd/notify-split-brain.sh root";
> }
> 
> Is Stonith still necessary? How do I configure it? I tried once but My
> machine couldn't reboot because stonith process was blocking and I give
> up to use it.
> 
> Thanks
> Felipe
> 
> On Wed, Dec 19, 2012 at 3:43 PM, Digimer <lists at alteeve.ca
> <mailto:lists at alteeve.ca>> wrote:
> 
>     On 12/19/2012 06:21 AM, Felipe Gutierrez wrote:
>     > Hi everyone,
>     >
>     > I have a scenario that I disconnect my primary from the network
>     and the
>     > secondary assume, becaming primary. After this, I connect the younger
>     > primary, and both nodes became secondary(DRBD), or Slave on Pacemaker.
>     > It is because DRBD on younger Primary is Standalone and Outdated.
>     It is
>     > a split-brain scenario.
>     > How do I make to my Pacemaker take care of that?
>     > I read these
>     >
>     http://www.drbd.org/users-guide-8.3/s-split-brain-notification-and-recovery.html
>     > ,
>     >
>     http://www.drbd.org/users-guide-8.3/s-configure-split-brain-behavior.html#s-automatic-split-brain-recovery-configuration
>     > and I think I cannot configure only my DRBD resource. I believe I need
>     > to do something on my Pacemaker.
>     > I think Stonith is not a good idea too, because I can reconnect my
>     > younger primary machine.
>     >
>     > Thanks in advance,
>     > Felipe
> 
>     Stonith isn't just a good idea, it's required for safe operation.
> 
>     The moment that the two DRBD nodes are Primary and StandAlone, you have
>     a split-brain. Stonith protects against this by tell drbd to block and
>     call a fence against the lost peer when connection breaks. When the
>     fence succeeds, the surviving node knows that it's peer can't be Primary
>     anymore because it's been killed.
> 
>     If you are using Pacemaker, tell DRBD to use the 'crm-fence-peer.sh'
>     script. If you are using red hat cluster, use 'obliterate-peer.sh' or
>     'rhcs_fence'. In either case, this "hooks" DRBD into pacemaker or cman's
>     existing fence devices.
> 
>     --
>     Digimer
>     Papers and Projects: https://alteeve.ca/w/
>     What if the cure for cancer is trapped in the mind of a person without
>     access to education?
> 
> 
> 
> 
> -- 
> *--
> -- Felipe Oliveira Gutierrez
> -- Felipe.o.Gutierrez at gmail.com <mailto:Felipe.o.Gutierrez at gmail.com>
> -- https://sites.google.com/site/lipe82/Home/diaadia*


-- 
Digimer
Papers and Projects: https://alteeve.ca/w/
What if the cure for cancer is trapped in the mind of a person without
access to education?