Recommended setup with large cache memory

[Attila Nagy]

Sami Kerola wrote:
> I am ISP hostmaster and we have DNS that gets resolver queries 
> about 4 million / 10 minutes at day time. There's eight servers 
> behind load balancer. Performance tuning options are set like 
> this:
We have about the same load, but currently only four uniprocessor servers.

>          max-cache-size 1024M;
>          cleaning-interval 15;
>          max-cache-ttl 604800;
>          max-ncache-ttl 300;
>          interface-interval 0;
>          recursive-clients 4096;
Don't you notice peaks every 15 minutes? BTW, now when it turned out 
that bind really can limit its cache usage, without cleaning, what is 
the rationale to use it?

> One of the tricks to keep cpu time in reasonable limits is to use 
> compile time option ISC_MEM_USE_INTERNAL_MALLOC like this:
What operating system do you use?

> With configuration above I see resolvers that don't crash, drop 
> packets and use about 10-20% of cpu time. The cpu is two times AMD 
Yes, bind is a CPU hog. :(

> Opteron(tm) 1800 MHz. In startup there is option -n 2 used. Cache 
> size seems to be on every resolver about 500 megabytes and stays 
> in that figure day after day.
I have made some benchmarks with and without threading and even bind 
9.3.1 is faster without it. Did you try to compile without threading?

BTW, did anybody thought about having a different caching (and even 
authoritative) backend, for example a memcached, spreading many machines?

You have 8 caches, I have 4. Each of them builds its own cache and the 
hit ratio goes down as you install more machines. A shared cache could 
be much more effective.

-- 
Attila Nagy                                   e-mail: Attila.Nagy at fsn.hu
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