michael@??? probably said:
> I noticed a large performance gain back then when I installed a caching
> name server. I advise you not to use forwarders, which avoids problems
> with locally screwed up delegations, if there are any.
Being part of our networking group and the person who runs the local
name servers, I cringe when I see advice like that. It's exactly
what I _don't_ want people to do.
If you don't care about bandwidth and if you don't care about your
machine thrashing if it's performance is already borderline, you don't
care about performance gains from other local caches and you don't
care about allowing other people to benifit from that cached
information.
To my mind thats a lot of "ifs".
Particularly at my site I have several well run caching servers spread
around several networks (and two of those networks are places traffic
has to go past to get out to the Internet anyway) on several
campuses. Not using them would be a lose in performance for 99% of
people since they gain from the contents of that cache and the work of
recursive lookups being done elsewhere.
My experiments when I was running large mail servers (and other
people's in similar situations) has been that if you already have a
good caching name server on a local network there is negligable gain
and even a performance loss in adding a local cache. Less likely to be
a loss of that cache forwards to an existing local cache or if your
machine is very under-worked (when you are unlikely to worry about
small performace gains).
If you have a badly run local cache or no ethernet-local cache, thats
another matter (but also not a blanket statement).
Nigel.Metheringham@??? probably said:
> Unhelpfully... it depends!
> If you have a nearby (ie direct ethernet connected DNS server with
> sufficient resources) DNS server then its unlikely to make much
> difference and could possibly be slower to use a same machine server
> due to context switches.
Seconded.
> DNS servers need memory. If a local server would be pushed into swap
> then thats seriously bad.
and they need other system resources which are taken away from your
mail server, too.
> In theory a local ncsd or similar cache could be good. In practice
> they are evil and should be destroyed immediately :-)
Kill nscd. With prejudice.
P.
--
pir pir@??? pir@???
