Greg A. Woods writes ("Re: [Exim] Delivery optimization tips for large lists ?"):
> Leaving nscd enabled for caching host information while at the same time
> using BIND for host information causes exactly the kinds of problems
> that any duelling cache protocol implementations will bring. Don't do it!
A friend of mine works for an ISP. One of their big mail servers was
configured to (a) run nscd and (b) do reverse lookup on all incoming
SMTP connections. But, nscd is crap[tm] and serialises all its DNS
queries, giving rather unhelpful behaviour: you didn't get 220 until
everyone in the queue in front of you had had their crap nameservers
timed out on. nscd could in principle not serialise requests, and use
the DNS TTL values, but that's probably too much hard work for Sun.
(Plug: fed up with libresolv ? Try my resolver library, currently in
alpha.
http://www.chiark.greenend.org.uk/~ian/adns/ )
Ian.
