On 2018-07-05 11:27 AM, Gianluca Cecchi wrote: > 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 I always prioritize simplicity and isolation, so I vote fore 2x 2-nodes. There is no effective benefit to 3+ nodes (quorum is arguably helpful, but proper stonith, which you need anyway, makes it mostly a moot point). Keep in mind; If your services are critical enough to justify an HA cluster, they're probably important enough that adding the complexity/overhead of larger clusters doesn't offset any hardware efficiency savings. Lastly, with 2x 2-node, you could lose two nodes (one per cluster) and still be operational. If you lose 2 nodes of a four node cluster, you're offline. -- Digimer Papers and Projects: https://alteeve.com/w/ "I am, somehow, less interested in the weight and convolutions of Einstein’s brain than in the near certainty that people of equal talent have lived and died in cotton fields and sweatshops." - Stephen Jay Gould