[CentOS] two 2-node clusters or one 4-node cluster?

Thu Jul 5 19:07:29 UTC 2018
Alexander Dalloz <ad+lists at uni-x.org>

Am 05.07.2018 um 17:27 schrieb Gianluca Cecchi:
> Hello,
> I'm planning migration of current two clusters based on CentOS 6.x with
> Cman/Rgmanager going to CentOS 7.x and Corosync/Pacemaker.
> As the clusters and their services are on the same subnet, and there no
> particular security concerns differentiating them, I'm also evaluating the
> option to transform the two clusters into a unique 4-node one during the
> upgrade.
> Currently I'm testing a virtual 4-node CentOS 7.4 cluster inside oVirt 4.2
> and things seem to behave well.
> Before going further in deep with tests and so on, I'd like to check with
> the community about how many CentOS 7.x clusters composed by more than two
> nodes are in place and what are the feedbacks on them in terms of
> incremented latency/communication, ecc scaling out.
> Also general feedback related to CentOS 6 and scalability of cluster nodes
> number is welcome.
> Thanks in advance,
> Gianluca

 From my point of view such classical cluster setups are so 2000s. 
Outdated by modern infrastructure concepts you see implemented in 
Kubernetes, OpenShift or cloud solutions in general. It's commonly 
summarized in the phrase "pets versus cattle". You don't want clusters 
to be treated as pets. Has always been difficult to maintain.

Obviously I don't know what you run on your old cluster and whether you 
can migrate to a modern setup instead of replicating it on a current 
major release. You didn't give us details.