From the “MySQL Performance Blog”:
So to get best possible performance our advise is still the same – you should try to fit your active dataset into memory, and it is possible as nowadays systems with 300GB+ RAM already available.
Conclusion is kind of obvious, but don’t think this is a MySQL/RDBMS advice only: check the Foursquare MongoDB outage post mortem post to see the impact of having to go to disk for each request). On the other hand, even if compelling from a performance point of view, I’m not going to say that it is doable or worth it (yet/ever?) to have all your data in memory.
Original title and link: More Memory or SSD? (NoSQL databases © myNoSQL)