for various reasons I run 3 pi-hole's and the router assigns these 3 pi-holes correctly as dns servers via dhcp. I thought this setup would ensure that even if 2 of the pi-holes go down everything would still work.
However as this is not the case I was looking around for some solution to make the setup high-availability (which to my limited understanding is having X instances of the same thing allowing X-1 things to die and the whole setup will still work), but all the conversations about it seem to devolve to discussion about how to sync the settings between the pi-holes. I already have this set up, all the 3 pi-holes are identical as they run in docker.
What I'm looking for is having only 1 IP for dns, which would automatically forward the dns request to any of the 3 pi-hole's that are up. Is that not high-availability? If so, then what is the thing I'm looking fo called?
I only run into this issue 1 day a week when the raspberry devices are being backed up, which shuts down all services takes a image of the sd-card and restarts all services. The backups are staggered and 2 out of 3 pi-holes are always up, but during the 3 or so hours on saturday the backups are running I often get warning e-mails from various hosts where various services complain about losing internet connectivity.
What would be the most noob-friendly way to make the system failover to next pihole seamlessly when 1 pihole dies?
Sorry if it doesn't make much sense, I'm not all that technical when it comes to concepts like this.