On 13/01/12 07:54, Fabio M. Di Nitto wrote:
On 1/12/2012 7:17 PM, David Teigland wrote:
It's a free-for-all without a list of allowed nodes.
I think i can understand your use case here, but my question is why is
quorum in charge of that?
My point here is not about quorum (although this helps us when we do talk
about quorum.) This is just about defining what the cluster is.
I understand what you want, but what I don´t understand is how it helps
quorum (see below).
Remember that this is not cman and that cman
had 2 functions, one of membership management (that's the one you are
really looking for, by allow/disallow a node) and quorum (calculated
after membership management has kicked in).
Right, both are important.
Maybe that's an important point that we've not drawn out yet. The list of
nodes also operates as a "permission list". Any node that's not listed
cannot join the cluster. I don't need to worry about some random or old
node coming along and intruding.
If anything, this has to happen either before quorum (at totem level or
in between), or at a much higher level (application that care do it
basically) since corosync doesn't really care, nor does pacemaker or the
quorum module.
I'm trying to make the argument that a node list is a good thing by
itself, apart from the benefits it has for quorum.
Same here....
I am not arguing that your point is valid or not (nodelist, membership
management etc). What I don´t understand, and that makes me think that I
am missing a use case, is (always put aside one second the
expected_votes use case, we discussed at length and we don´t disagree
there):
why is a nodelist *technically* important for quorum?
how does quorum benefits from this list?
how should this list be used by quorum?
I node list is NOT technically important for quorum. VMS manages quite
happily without one - it builds up the node list at run-time as nodes
join the cluster. They need a security key to do so but no other
pre-configuration is needed if they have their own system disk (most VMS
clusters are single system disk, but it's not a requirement).
cman in RHEL4 didn't need a pre-defined nodes list, it was designed not
to need one. It's only the requirement of the higher layers that
mandated it. In fact you can run cman in RHEL4 and RHEL5 without any
nodes list if you don't need fencing. 'cman_tool join -X'
In several emails you write that the list is important/vital/etc. for
quorum, but I am not getting it.. i simply don´t understand what you are
trying to communicate me and I´d really like to understand and in case
fix the code.
Fabio
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