1. Temporary tables created on disk is always around 40-45% no matter what values I chose for tmp_table_size and max_heap_table_size. Currently, they are at 256M, mysqltuner suggested to reduce the values, tuning-primer suggested to increase the values. I tried both, still got 40-45%. Total fragmented tables is also quite high: 170.
2. I have key_buffer_size=128M, I saw some people got it as high as 768M. But tuning-primer suggested to lower the value. Should I trust tuning-primer? What are the reasons for setting key_buffer_size value high? I am using Enhanced Search if that matters.