On: Your data fits in RAM

[mhaymo]

Does your RDBMS's built-in caching not handle this pretty well? Just up the cache size, e.g. in PostgreSQL changing effective_cache_size https://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Serv...

[SwellJoe → mhaymo]

For reads, yes. It's fine on reading data. The problems are writes which always wait for disk consistency to return.

[nierman → mhaymo]

shared_buffers is the setting you're thinking of here.

effective_cache_size should be set to a reasonable value of course, but it does not affect the allocated cache size, it's just used by the query optimizer.