I’m curious how horizontally scalable xtraDB is? In other words, what if I had a single cluster where the nodes were configured with 8xCPU and 32GB RAM, coupled with 10Gbps in a LAN between the nodes … how many nodes are capable in the cluster? Is it unreasonable to consider 9 nodes or would that generate too much overhead for sync or some other factor? I do realize I’m giving a scenario where not all factors are discussed. Also, let’s assume the DB had ~250 tables for the configuration.
The most important factor in PXC is latency between the nodes, and number of nodes.
Since each node needs to communicate and certify withe every other, overhead due to this increases exponentially as you add nodes. On most cases, 3 to 5 node works, up to 7 in some circumstances, but more than that the overhead would be counter productive. Depending on server load, you might need to consider other strategies such as vertical scaling, sharding, async replica.
Do note that PXC favors data consistency and high availability at the cost of performance. So, depending your needs you might need to escalate pxc or resort to other ways