All Pi-Hole servers should be updated to enable DNS over HTTPS

Hide your DNS queries from your ISP!

https://docs.pi-hole.net/guides/dns/dnscrypt-proxy/

Remove rate limit on pi-hole

Edit /etc/pihole/pihole-FTL.conf

Change RATE_LIMIT line to:

RATE_LIMIT=0/0

then restart pi-hole:

sudo service pihole-FTL restart

You won't see random DNS resolution issues again!

Fix pi-hole disk keep getting full

Unfortunately, the default setting of pi-hole allows small pi-hole installations to fail due to disk getting full. The FTL database file /etc/pihole/pihole-FTL.db captures logging for 365 days by default, and it can grow to multi-gigabytes within that period.

First, stop the service:

sudo service pihole-FTL stop

If your disk is already full, first delete the pihole-FTL.db file by doing:

sudo rm /etc/pihole-FTL.db

Then edit maxDBdays configuration in your /etc/pihole/pihole.toml file as follows:

1. sudo vi /etc/pihole/pihole.toml
2. Fine the line maxDBdays = xxx and change xxx to 30 (or something smaller from the default 91)
3. :wq command to save and quit vi

And start the service:

sudo service pihole-FTL start

That should allow your pi-hole installation to operate for a long time. FYI I see about 300MB pihole-FTL.db size after 30 days in my home network.