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Asif ali Ali avatar Server

Bind9 DNS rate limit or QPS optimization

ma flag
Asif ali Ali

Hello everyone hope you all fine, I am working on DNS bind on centOS 7, need to optimize, in our environment currently 30000 to 40000 qps checked by dnstop command, at peak hours DNS start dropped some queries, kindly advise how to optimize my DNS to perform maximum QPS by utilizing VM resources to avoid from dropping queries in peak hours, DNS virtual machine resources 32G RAM 16CPU's, we have to optimize our DNS to perform 60000 to 80000 Queries per second kindly guide...

Here is my DNS bind configuration..

options {

    listen-on port 53 { 127.0.0.1;  x.x.x.x; };
    listen-on-v6 port 53 { any; };

    directory       "/var/named";
    dump-file       "/var/named/data/cache_dump.db";
    statistics-file "/var/named/data/named_stats.txt";
    memstatistics-file "/var/named/data/named_mem_stats.txt";
    recursion yes;
    allow-query { clients; };

    allow-recursion { clients; };

    allow-query-cache { clients; };

    allow-transfer { "slaves"; };

    tcp-clients 2000;
    additional-from-cache no;
    dnssec-enable no;
    dnssec-validation no;
    dnssec-lookaside auto;
    auth-nxdomain no;
    max-cache-size 10000m;
    max-ncache-ttl 86400;
    max-cache-ttl 259200;
    recursive-clients 80000;
    check-names master ignore;
    check-names slave ignore;
    check-names response ignore;
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us flag
Rob
My first impression is that 40.000 queries per second is quite a lot and with such a load ISC Bind may not necessarily be the first limiting factor or primary bottleneck . Other OS and/or network limitation may have been reached. Are you monitoring those already? Is your server an authoritative or recursive name server or both? If is both - split those roles. If it is authoritative: consider increasing default TTL's (that has several performance benefits). Of interest: https://kb.isc.org/docs/bind-best-practices-authoritative
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us flag
Rob
`max-cache-size 10000m;` seems a bit low for a system with 32 GB of RAM memory https://bind9.readthedocs.io/en/v9_16_4/reference.html#server-resource-limits
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Patrick Mevzek avatar
cn flag
Patrick Mevzek
Separate recursive and authoritative functions. Then you can optimize each part separately. Recursive should be pretty easy to scale by adding more servers.
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