Cache DNS servers
PowerDNS is really fast, I’d also evaluate “unbound” as caching server. You can use powerdns’ loadbalancer “dnsdist” in front of whatever you end up using. All these are free.
> Concur 100%.
> You may also wish to consider two layers of caching – e.g., an aggregate cache in addition to caching on user-facing caches, along with dedicated resolvers. See this .jpg diagram:
Tested similar topologies in anger and haven’t found that the benefit (which is fairly small) is worth it for the added complexity. I find that unbound with large cache sizes works very well – https://www.unbound.net/documentation/howto_optimise.html <https://www.unbound.net/documentation/howto_optimise.html> is a good primer. Collect stats with collectd and the unbound collectd python module from here:
We get the stats out the end of our stats pipeline with Grafana, and have a detailed analytics dashboard that give us hints about what needs to be looked at. We chart queries per CPU%, recursion times, all sorts of good stuff.