I am the Director of Product Management for MemSQL.
The 128 GB limit applies to the whole cluster. So if you have two nodes in the cluster they would each have to be 64GB or less. If you have four nodes they would all have to be 32 GB or less. To have a highly available system we recommend 4 nodes (a master aggregator, a child aggregator and two leaf nodes). You can read more about the cluster architecture here: https://docs.memsql.com/concepts/v6.7/distributed-architectu...