[Flounder] DNS Caching Server

[Russell Coker]

On Friday, 27 May 2022 06:02:06 AEST DL Neil via Flounder wrote:
> On 26/05/2022 20.53, Russell Coker via Flounder wrote:
> > On Wednesday, 25 May 2022 18:46:50 AEST DL Neil via Flounder wrote:
> >> Am most used to dnsmasq (local network and VMs).
> >> 
> >> SpamAssassin + DNS-WhiteList/BlackList docs say to use a DNS caching
> >> server, but specifically-not dnsmasq.
> > 
> > Why do they recommend not dnsmasq?
> 
> «Dnsmasq should not be used by SpamAssassin since it can only forward to
> other DNS servers.»
> https://cwiki.apache.org/confluence/display/spamassassin/CachingNameserver

That's not a reason to not use it.  Running a caching server that talks to a 
single other server is a relatively common configuration.

> >> VPS resources are OK, but CPU probably of most concern.
> >> 
> >> Seeking recommendations based on your use/experience, eg unbound, bind,
> >> ..., please?
> > 
> > BIND has always worked for me.
> 
> Yes, but it 'does it all', and is more resource-hungry - or as some say:
> over-large/bloated.

https://doc.coker.com.au/papers/benchmarking-mail-relays-and-forwarders/
https://etbe.coker.com.au/2021/05/03/dns-lots-ips-postal/

In 2006 I presented a paper on benchmarking mail relays and forwarders which 
surprisingly showed that BIND as a name server was a major bottleneck.  At the 
time I didn't investigate any other DNS caches as the mail server software was 
my main focus.  In 2021 I repeated the same tests on bigger hardware and found 
that DNS wasn't a bottleneck at all.

My conclusion is that if you do this sort of thing on hardware that was 
affordable in 2006 then the performance of the DNS server is an issue.  But if 
you use it on affordable hardware in 2021 then it's no big deal.

As for the servers I run at the moment, my email is currently stored on a 
server with hard disks and that is obviously the bottleneck.  In a year or so 
it will be on a server with NVMe and there won't be any bottlenecks.

-- 
My Main Blog         http://etbe.coker.com.au/
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