Hello Cassandra community, We are trying to upgrade our systems from Cassandra 3 to Cassandra 4. We plan to do this per data center. During the upgrade, a cluster with mixed SW levels is expected. At this point is it possible to perform topology changes? In case of an upgrade failure, would it be possible to remove the data center from the cluster, restore the datacenter to C*3 SW and add it back to cluster which will contain datacenters in both C* 3 and C*4? Alternatively, could we remove the datacenter, perform the SW upgrade to C*4 and then add it back to the cluster? Are there any suggestions or experiences regarding this fallback scenario?
BR MK
