There are a number of points to consider when deciding on a node configuration, including disk sizes, memory requirements, and the number of processor cores. The right choices depend quite a bit on your use case and whether you are on a physical or virtual infrastructure, but we will discuss some general guidelines here.
Since Cassandra is designed to be deployed in large-scale clusters on commodity hardware, an important consideration is whether to use fewer large nodes or a greater number of smaller nodes.
Regardless of whether you use physical or virtual machines, there are a few key principles to keep in mind:
More RAM equals faster reads, so the more you have, the better they will perform. This is because Cassandra can take advantage of its cache capabilities as well as larger memory tables. More space for memory tables means fewer scans to the on-disk SSTables. More memory also results in better file system caching, which reduces disk operations...