Recommended setup with large cache memory
Attila Nagy
bra at fsn.hu
Fri Sep 9 09:37:58 UTC 2005
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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