Apple – Support – Discussions – Manually provided DNS server addresses …. This is not official but it has been my experience as well. Even better is to just avoid any DNS server that is questionable.
Then you will probably want to read this interesting article. Click here. Or you can read the summary “We can only recommend larger capacities of 8 GB to 12 GB for professional applications where its usefulness has already been documented and for servers. None of our tests required high-memory capacities and wasted RAM is a burden both financially and ecologically.”