Not necessarily true. If you're sharing the database with your transaction workload your cache will be paged out eventually.
This was my take as well, but I'm a MySQL / Redis shop. I really have no idea what tables MySQL has in RAM at any given moment, but with Redis I know what's in RAM.
This was my take as well, but I'm a MySQL / Redis shop. I really have no idea what tables MySQL has in RAM at any given moment, but with Redis I know what's in RAM.