Increase max-cache-size

[Prabhat Rana]

Thanks for a quick response. We increased the max-cache-size to 2048M because we still have 28GB free memory out of 32GB and we noticed performance improvement right away. 
So I have few questions regarding cache. Is there anyway we can check whether or not cache is full? what happens once the cache of 2048M is filled. It doesn't cache anymore and it forwards the lookups to the internet for a query that is not in cache for every query?
How does cache space become available again?
Thanks
Prabhat

--- On Mon, 7/28/08, Alan Clegg <Alan_Clegg at isc.org> wrote:
From: Alan Clegg <Alan_Clegg at isc.org>
Subject: Re: Increase max-cache-size
To: prana9533 at yahoo.com, "DNS BIND" <bind-users at isc.org>
Date: Monday, July 28, 2008, 8:34 PM

Prabhat Rana wrote:
> I'm running BIND 9.5.1b1 on Solaris 10. Initially I didn't have
any 'max-cache-size' parameter set in named.conf. When I was getting
1500 or more rercursive clients at any given time according to 'rndc
status', I noticed some latency in recursive requests. I added the
'max-cache-size  500M;' and that seemed to help the latency because the
number of lookups to the internet was reduced due to most of the request being
fulfilled by the cache. I still have 25G Memory free. So my questions are. 
> Where does the named cache sit? in memory? 
> What is the max-cache-size by default?
> What is the max value I can assign for cache?
> I understand if I increase the size of cache it increases the security
risks for cache poisoning. But I need to increase is so that as much possible
queries are served by the cache
> Any help would be greatly appreciated.

In BIND 9.5, default max-cache-size is 32M.

Max is "0" which will allow the cache to grow to fill all available
memory.

There is no additional risk of cache poisoning based on larger cache.

AlanC