[Pdns-users] Recursor Cache Sizing: Is more always better?

Christoph cm at appliedprivacy.net
Tue Sep 12 11:35:17 UTC 2023

Hi Winfried,

> My recommendation is to limit the TTL to 12 or 6 hours and find out
> how many cache entries are created during this time. Increase that by
> 50% and that's your value. 

thanks for your recommendation. I've played a bit with this to see what
max-cache-entries values this procedure would result in.
What input should influence whether this should be done with a 
max-cache-ttl of 6, 12 or 24 hours?

The change to max-cache-ttl [1] to N hours would just be temporary, 
during the collection of the cache-entries metric, and be set back to 1d 
(default) after that or stay at N hours?
Should this procedure be done with refresh-on-ttl-perc=0 for the data 
gathering phase?

In any way, the approach results in a significantly larger 
max-cache-entries setting than we currently use.

Does the same apply to other caches like
aggressive-nsec-cache-size and
dnsdist's packetCache maxEntries?


[1] https://doc.powerdns.com/recursor/settings.html#max-cache-ttl

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