Is your list not entirely depending on the usecase?
I am using ES for years with over 1 million daily users.
It provides simple search funtionality.
it runs on a single node with 4gb of memory. For more than 5 years with hardly any issues.
If the dataset it fits on one node - good. You might still be missing out on reliability (should that node fail or just plain restart).
Simple catalogs and/or web pages search usually fit in RAM, so the advice of disk:ram becomes less relevant, also the type of drive would be mostly irrelevant.
