Hi @all,
I am running a current pihole installation on a Pi 3 model B using unbound to self-resolve hostnames. The link to my router (acting as broadband modem and DHCP server) is wired, 100Mbit/s. The router/PI are serving on average 6-10 local clients.
Now, I have some spare gigabit ethernet USB dongles laying around that I could use to connect the Pi with gigabit speed.
Is this worth doing? Traffic for DNS queries is minimal and I wonder if higher bandwidth even makes a difference.
If I swap the interface over to the external dongle, how would I tell raspbian and pihole about the different interface?
Impact on DNS resolution will be minimal. (click for details)
Assuming a 1 KB DNS message size (most are smaller), approx. theoretical transfer speed would drop from ~90 to ~9 microseconds, or from 0.09 to 0.009 milliseconds (ms).
That will be superimposed by your ethernet latency fluctuating between 0.x and 3 milliseconds, completely blurring any performance gains for DNS.
You may be able to measure it, but it won't be perceivable.
Updating Pi-hole or your OS may be faster, but only if your ISP download link is well above your RPi 3B's current 100Mbit/s speed.
If your RPi's sole purpose is hosting Pi-hole, I wouldn't bother.
Find a better use for your spare Gbit dongles.
My internet DL speed is not above 100Mbit/s - and even then I wouldn't care if updating Raspbian or pihole takes a minute longer.
I guess I will equip a Pi Zero (non Wifi) with it to have backup resolver. Last week someone accidentally cut power to my Pihole and everything was offline (except for some dirty browsers that don't respect system network settings and think they can do DNS resolving on their own...).
A second Pi (2-3 W power consumption?) should greatly reduce likelyhood DNS service being down.