Re: [Exim] Long lookup time - almost solved now

> michael@??? probably said:
> > I found that a local, caching only BIND increases overall performance
> > a lot. Note that you will not see the difference on smaller systems.
> > I put 127.0.0.1 as first nameserver in resolv.conf and our central
> > caching nameservers as secondary nameservers. That way I can restart
> > the local BIND without interrupting regular operation, e.g. to get
> > rid of the cached records, but usually I enjoy very short latencies.
>
> This topic is somewhat religious and somewhat misleading.

I wondered if I should mention that it has been discussed before. ;-)

> If you have a shortage of memory or a very busy mailserver the extra
> memory usage and extra context switches of a nameserver on the same
> machine can impact performance negatively.

Extra memory is a point, but did you actually see the context switch
problem? If so, I would be interested in details.

> Personally I prefer to have the nameserver on a different machine
> which is very close network wise (same local subnet).

I had that and a local server reduced latency a lot. This is a switched
full duplex 100 Mbit/s Ethernet.

> If a local cache does make things better then I would recommend
> forward-first to another local cache, so you get the benifit of the
> local cache but the local machine doesn't have to do as much work (and
> it benifits from the cache on the other machine).

Then again, if the remote BIND goes down, you have a problem. This is
a particularly religious matter. I guess we can agree that everybody
should think about it and then decide. :)

Michael