[ClusterLabs] About Corosync up to 16 nodes limit

Digimer lists at alteeve.ca
Wed Jul 5 23:45:05 EDT 2017

I'm not employed by Red Hat, so I can't speak authoritatively.

My understanding, however, is that they do not distinguish as corosync
on its own doesn't do much. The complexity comes from corosync traffic
though, but it gets more of a concern when you add in pacemaker traffic
and/or the CIB grows large.

Again, there is no hard code limit here, just what is practical. Can I
ask how large of a cluster you are planning to build, and what it will
be used for?

Note also; This is not related to pacemaker remote. You can have very
large counts of remote nodes.


On 2017-07-05 11:27 PM, mlb_1 wrote:
> Is RedHat limit node's number, or corosync's code?
> At 2017-07-06 11:11:39, "Digimer" <lists at alteeve.ca> wrote:
>>On 2017-07-05 09:03 PM, mlb_1 wrote:
>>> Hi:
>>>       I heard corosync-node's number limit to 16? It's true? And Why?
>>>      Thanks for anyone's answer.
>>>  https://specs.openstack.org/openstack/fuel-specs/specs/6.0/pacemaker-improvements.html 
>>>   * Corosync 2.0 has a lot of improvements that allow to have up to 100
>>>     Controllers. Corosync 1.0 scales up to 10-16 node
>>There is no hard limit on how many nodes can be in a cluster, but Red
>>Hat supports up to 16. SUSE supports up to 32, iirc. The problem is that
>>it gets harder and harder to keep things stable as the number of nodes
>>grow. There is a lot of coordination that has to happen between the
>>nodes and it gets ever more complex.
>>Generally speaking, you don't want large clusters. It is always advised
>>to break things up it separate smaller clusters whenever possible.

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