I am running on a machine with 16 GB of memory.  I am thinking that the bigger MemtableSizeIbMB, the more data will be kept in memory so there will be less disk I/O.  Can I eliminate disk I/O all together if all my data fits inside Memtable?  My application is constantly inserting new data and remove old ones.  Will keeping everything in Memtable generate so much garbage collection activity that it would impact performance?