[Pacemaker] A/P Corosync, PGSQL and Split Brains questions

[Stephan-Frank Henry]

> On: Fri, 11 Feb 2011 01:54:04 +0100, Lars Ellenberg worte:
> On Wed, Feb 09, 2011 at 02:48:52PM +0100, Stephan-Frank Henry wrote:
> > My scenario:
> > Acive/Passive 2 node cluster (serverA & serverB) with Corosync, DRBD &
> PGSQL.
> > The resources are configured as Master/Slave and sofar it is fine.
> > 
> > Since bullet points speak more then words: ;)
> > Test:
> >  1) Pull the plug on the master (serverA)
> >  2) Then Reattach
> > Expected results:
> >  1) serverB becomes Master
> >  2) serverB remains Master, serverA syncs with serverB
> > Actual results:
> >  1) serverB becomes Master
> >  2) serverA becomes Master, data written on serverB is lost.
> 
> Without logs, it does not make much sense to guess what may have
> happened, and why.
> 
> >   net {
> >     cram-hmac-alg sha1;
> >     after-sb-0pri discard-zero-changes;
> >     after-sb-1pri discard-secondary;
> 
> 
> This is configuring data loss.
> Just because during some connection handshake, after a split brain,
> one node is currently secondary, does not necessarily mean that is the
> data set you want to throw away.

Yes, that does make sense.