Adding more CPU and RAM to existing vmselect nodes improves the performance for heavy queries, which process a big number of time series with a big number of raw samples. The cluster stability is also improved with the number of vmstorage nodes, since active vmstorage nodes need to handle lower additional workload when some of vmstorage nodes become unavailable. It is preferred to add more vmstorage nodes over adding more CPU and RAM to existing vmstorage nodes, since higher number of vmstorage nodes increases cluster stability and improves query performance over time series with high churn rate.