ROS cache size and Key-Value queries
Hello. As I know there are two types of cache vertica uses while reading data from disk:
- a file system cache
- and a cache of uncompressed data blocks (ROS cache) Vertica maintains internally to avoid decompression on blocks reused quickly.
They mentioned at MC MonitoringSystemMemoryUsage page:
My concern is related with key-value queries. Generaly I see them performing on 300ms per query. But sometime there is a 4-10 seconds skipe. And if I rerun that kind of query after a skipe I get the same 300ms performance. I belive it is somehow connected with disk skan operations and cache failure.
Does anybody know the query MC is using to determine ROS cache size? Are there any setting available for ROS cache?