Hi Vishal, In Cassandra 3.11.2, there are 3 choices for the type of Memtable > allocation and as per my understanding, if I want to keep Memtables on JVM > heap I can use heap_buffers and if I want to store Memtables outside of JVM > heap then I've got 2 options offheap_buffers and offheap_objects.
Heap buffers == everything is allocated on heap, e.g the entire row and its contents. Offheap_buffers is partially on heap partially offheap. It moves the Cell name + value to offheap buffers. Not sure how much this has changed in 3.x Offheap_objects moves entire cells offheap and we only keep a reference to them on heap. Also, the permitted memory space to be used for Memtables can be set at 2 > places in the YAML file, i.e. memtable_heap_space_in_mb and > memtable_offheap_space_in_mb. Do I need to configure some space in both heap and offheap, irrespective > of the Memtable allocation type or do I need to set only one of them based > on my Memtable allocation type i.e. memtable_heap_space_in_mb when using > heap buffers and memtable_offheap_space_in_mb only when using either of the > other 2 offheap options? Both are still relevant and used if using offheap. If not using an offheap option only memtable_heap_space_in_mb is relevant. For the most part, the defaults (1/4 of heap size) should be sufficient.
