[Pacemaker] Quorum in pacemaker

[Vijay B]

Hi Emmanuel,

Thanks for the response! I thought cman is a newer version of corosync
itself, w.r.t the plugin that is used between corosync (cluster membership)
and pacemaker (resource group management) - is that not the case? I
installed the pacemaker and cman packages on ubuntu 12.04, and no package
like "corosync", and yet I see /etc/corosync/corosync.conf get created post
cman installation - so what is the difference between these two? If running
cman is not the same as running corosync, what am I doing here and what am
I not understanding correctly?

Thanks,
Regards,
Vijay


On Thu, Jun 26, 2014 at 5:47 PM, emmanuel segura <emi2fast at gmail.com> wrote:

> {I'm trying to set up a three node cluster using pacemaker+corosync} =
> but you trying to use cman, depending on your distro you can use
> different cluster es: cman + pacemaker or corosync+pacemaker
>
> 2014-06-27 2:22 GMT+02:00 Vijay B <os.vbvs at gmail.com>:
> > Hi,
> >
> > I'm trying to set up a three node cluster using pacemaker+corosync, and I
> > installed the required packages on each node, checked for their network
> > connectivity so they can see each other, added the required startup
> scripts
> > and edited the cluster.conf file as well so it includes all three nodes.
> >
> > Now, when on the first node, I attempt to start up cman using service
> cman
> > start, it times out thus:
> >
> > vagrant at precise64-pmk1:~$ sudo service cman start
> >
> > Starting cluster:
> >
> >    Checking if cluster has been disabled at boot... [  OK  ]
> >
> >    Checking Network Manager... [  OK  ]
> >
> >    Global setup... [  OK  ]
> >
> >    Loading kernel modules... [  OK  ]
> >
> >    Mounting configfs... [  OK  ]
> >
> >    Starting cman... [  OK  ]
> >
> >    Waiting for quorum... Timed-out waiting for cluster
> >
> > [FAILED]
> >
> > vagrant at precise64-pmk1:~$
> >
> >
> > Why is this? Is it because I have three nodes to begin with in my
> > /etc/cluster/cluster.conf, and so this node expects that the cluster
> quorum
> > is 2, and so it should be able to talk to at least one other node? At
> this
> > point, I haven't started the cman or pacemaker services on the other
> nodes.
> >
> > If this is the case, what will happen when two nodes of the three die? In
> > case cluster.conf changes accordingly to reflect the new cluster
> membership,
> > what if all three nodes are simply powered off and one rebooted? The
> cluster
> > will be down, won't it?
> >
> > What is the best way to get around this? I don't want to set
> > CMAN_QUORUM_TIMEOUT=0, since as I understand it, the node would then go
> > ahead and start itself as a cluster without waiting for the other nodes,
> and
> > if this causes my service to start up and it is already started/running
> on
> > another node, it could cause issues.
> >
> > Now, I don't know how to configure quorum disks for pacemaker - is it
> > possible to do this with pacemaker? How does it work? What are the
> > recommended ways to address the above problem? I infer that if this disk
> is
> > configured, the node that grabs the disk first becomes the president of
> the
> > pacemaker cluster. In this context, I have another question - does
> corosync
> > have its own cluster membership state distributed across all cluster
> nodes?
> > If so, I guess quorum is configured at the corosync level rather than at
> the
> > pacemaker level?
> >
> > Apologies in advance if my queries above are addressed in the
> documentation
> > already - I felt it would be quicker and more accurate to ask the
> community
> > for reliable info.
> >
> > Thanks!
> > Regards,
> > Vijay
> >
> >
> >
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> >
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> >
>
>
>
> --
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>
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