I am using Unbound and Cloudflare to add Pi-hole with address 127.0.0.1. When I restarted the device, I found that Unbound and Cloudflare were delayed about 4-5 minutes before performing DNS resolution.
Fortunately, my ISP already has IPv6 so I added Google IPv6 DNS to backup. Every time I restart the device, Pi-hole can still resolve normally without delay. But so my DNS queries can be switched to Google servers for random resolution (if query times are faster than Unbound and Cloudflare).
In the future, can the Pi-hole add the DNS fallback feature to backup every time Unbound or Cloudflare can't boot every time the device is turned on?
As mentioned by @ajp2k17 quote
Interesting idea running both Unbound and Knot in parallell /quote
Read the topic here. Contains method to compile unbound from source and configuration files for unbound.
Read how to install knot resolver here. Select Add repository and install manually. Sample configuration file provided in the topic, mentioned above.
I understand, but the problem is that dns resolution service does not run at the same time as pihole. Usually the pihole service will run first then unbound after running, delay about 2-4 minutes.
This has not been my experience with 4 Pi-Holes running 4 instances of unbound. Perhaps there is an interaction between unbound and Cloudflare that produces this delay.