Predicting Performance improvements from memory increase

(Peter Zaitsev) One common question I guess is how much should I see performance improved in case I increase memory say from 16GB to 32GB. The benefit indeed can be very application dependent - if you have working set of say 30GB with uniform data access raising memory from 16GB to 32GB can improve performance order of magnitude by converting very IO bound load to CPU bound, it is well possible to see limited gains - if your working set already fits in 16GB you may not see any significant gains upgrading memory to 32GB. Interesting enough similar can happen for very large working set - for example if your main queries do full table scan of 100GB table it does not matter if you have 16GB or 32GB the load is going to be way too much IO bound anyway.