[Pdns-users] Questions about PowerDNS - CNAME at APEX, Capacity, management, etc...

Jake jake at elsif.net
Fri May 6 15:12:52 UTC 2022

Some questions ranging from "anyone can answer" to "only high rollers will 
have this insight"...thank you for indulging me and for any guidance you 
might be able to provide.

General questions:

Does PowerDNS load all of the zones into memory, and then start serving 
(like BIND), or does it load each zone and start serving said zone 
immediately upon load (like KNOT)?

When in "secondary" mode, how does PowerDNS select which "primary" to 
retrieve a zone from?  Is it based on the configured list, is it based on 
performance, or is it based on which server it first received a notify 

What's the best method for updating a backend with DNS changes in an 
instance where there are 6 million+ zones?  Assuming updating the database 
isn't the best method, what kind of volume can the API or dynamic update 
paths handle?  Is my assumption correct that I only have to worry about 
this in a "primary" configuration, and that a "secondary" configuration 
can rely entirely on standard zone transfers?

CNAME @ APEX questions:

Would I be right in my assumption that if one wants to use the CNAME @ 
APEX recursion hack, that the entire ecosystem (both distribution servers 
and cloud servers) would need to be PowerDNS to accomplish this, given 
that BIND and KNOT will not load a zone with CNAME @ APEX?

What about DNS software vendor diversity?  Anyone else out there doing 
CNAME @ APEX that you find is a good mix with PowerDNS?

Capacity questions:

Can a PowerDNS instance handle 6 million zones and 300 million records?

Does one backend perform better than the others at this capacity?

If operating a global anycast network, is the backend database sitting on 
the DNS server itself, or does one dedicate a node or two in each site as 
part of a backend database cluster?  How much does an on-server database 
impact query performance?

At what point do you hit the requirement for multiple backends?

Can anyone provide me a fuzzy number on RAM footprint?
example:  "I have $x million records, and that's using $y amount of RAM"

What is the startup timing on a large PowerDNS installation?
example:  "I have $x million records, and that takes $y minutes until 

Thanks again,

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