I have couple questions related to memory mapping of segment data:
- If a historical node is started will it proactively memory map segment data or does it happen only when a query occurs?
If it happens proactively, which segment on the historical node will be mapped if the memory/disk ratio is larger than 1?
If it doesn’t happen proactively is there a way to enforce memory mapping of segments after a cold start?
During some tests, I noticed that memory mapping seems to happen per metric and not per all segment data. Could you please shed some light on how memory mapping in Druid works in detail?
The tests show no significant difference in query latency between 1:1 and 1:2 memory/disk ratios. What is the memory/disk ratio recommended to use?