recursive-clients, what value ?

[Ladislav Vobr]

> Ahhh! That's good to know, I didn't realize the ServFail's weren't cached.
> Thanks for the info, I sure wish servfails were cached, as it stands, it's
> not hard to start a short lived DOS against a DNS farm that will recurse for
> you with bad servers and one bad domain. 
yes :-) I guess we all lernead it hard way :-)
>  
>>Richard, how can I plot cache hit rate? Do you mean rndc 
>>stats, there is 
>>only # of recursive requests.
>
> You can look at the # of recursive requests and the number of total requests
> to get the % of your requests that are answered from Cache. I found this to
> be amongst the most useful datasets when correlating machine performance
> with different configurations. It's not uncommon to see 75% of the queries
> on my farm answered out of cache during peak usage hours. I don't know or
> have exact numbers on how much longer a cached vs a non-cached query will
> take right now, but I do have direct performance differences.
> 
> Getting my cache hit rate up from ~50% to ~65% yeilded more than a 15%
> performance improvement, with only minimal changes to our configurations.

hmm, I thought there might be a relation, but seemed to me more 
complicated, what about the failures don't they initiate a query before 
they fail, is this failed query counted as well in recursion? and what 
is it recursion actually, when I dump stats I see recursion, imho 
caching server initiate on behalf of recursive clients non-recursive 
queries (unless it is forwarding), so if it counts how many 
non-recursive queries had to be done, because it was not cached, it 
should not be called recursion, but i might be wrong here:-), I think 
definitelly it is very good idea, to plot this. We are using rrdtool 
here but use to plot only basic stats, we'll try this parametr as well.

Thanks for your support

Ladislav