Based on my tuning work with C* over the last days, I guess I reached the following insights.
Maybe someone can confirm whether they make sense: The more heap I give to Cassandra (up to the GC tipping point of ~8GB) the more writes it can accumulate in memtables before doing IO. The more writes are accumulated in memtables, the closer the IO gets towards the maximum possible IO throughput (because there will be fewer writes of larger sstables). So in a sense, C* is designed to maximize IO write efficiency by pre-organizing write queries in memory. The more memory, the better the organization works (caveat GC). Cassandra takes this eagerness for consuming writes and organizing the writes in memory to such an extreme, that any given node will rather die than stop consuming writes. Especially I am looking a confirmation of the last one. Jan
