The important part of this recipe is starting with a viable estimate of the database size. Since a lack of RAM won't cause the database to crash or operate improperly, we can use looser guidelines to obtain this number. Hence, three years down the road, an existing database install could be eight times larger than its current size.
Why do we then divide that number by ten? Our goal here is to maximize the benefit of the OS-level cache, which will consume a majority of our RAM. This estimate gives us a value that is ten times smaller than the space our database consumes. At this scale, data that is frequently fetched from disk is likely to be served from memory instead. The alternative is read latency due to insufficient memory ...
