[Pdns-users] question about PDNS - performance

bert hubert ahu at ds9a.nl
Tue Feb 22 20:33:28 UTC 2005

On Wed, Feb 23, 2005 at 09:00:08AM +1300, Dan Clark wrote:
> I recently tried powerdns and was pretty astounded that it couldn't keep 
> up with my 30 odd zones.

Given that we have people with millions of domains on a relatively small
number of machines, this is probably not a PowerDNS problem. Which backend
did you use? Which operating system?

To Michiel, well, we've done a lot of different measurements. Some
configurations reach 50.000 queries per second. It all depends. For very
large zones, bind2backend will probably be the fastest. Especially
PostgreSQL can be very very very slow in the default configuration. This is
due to their defaults, not due to PowerDNS.

It is possible to configure your backend to get dismal performance if you
want to.

We have a rather large number of users doing >50.000 zones on single

> Once I did get it all going, queries took too long to return results and 
> reverse lookup zones didn't seem to work. Then after a day in service 
> the box would only answer queries from nslookup/dig on the box itself 
> and no longer from the interweb as it would time out before it could 
> answer the query.

Sounds a bit like:
    Q: PowerDNS does not answer queries on all my IP addresses and I've ignored
the warning I got about that at startup

    A: Please don't ignore what PowerDNS says to you. Furthermore, read
Chapter 15 about the local-address setting, and use it to specify which IP
addresses PowerDNS should listen on. 

from http://doc.powerdns.com/pdns-users-faq.html - that might cause this

I don't know of any reverse lookup problems - forward and reverse are not
different from the PowerDNS perspective, both just records.

> >We are hosting zones with a large amount of answers/queries per minute 
> >(at least  20.000 answers per.minute - 500 queries p/m)
> >This is for 1 zone..we are having 3 or 4 of this kind of customers 
> >which are having such a large DNS load.

PowerDNS does a lot of caching - if you look at typical queries, most will
be answered from the cache. Worst case performance is typically a lot worse,
but generally does not happen.

> >Can PDNS with Mysql (gmysql backend) handle this amount of load easily?
> >What is the MAX? I know it is also a hardware issue but we are currently
> >running this load on dual p 3 800 Mhz 512 MB Ram and 2 18,2 GB SCSI
> >disks).

If you run a dual cpu system, it is almost mandatory to run a recent Linux
distribution (2.6 kernel, recent glibc or for example a recent Fedora Core
or debian > sarge) to get decent performance.

MySQL is generally very fast, 500 qps is not a problem.

Good luck!

http://www.PowerDNS.com      Open source, database driven DNS Software 
http://netherlabs.nl              Open and Closed source services

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