Increase max-cache-size

[Prabhat Rana]

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.
Prabhat
TSE
Sprint/Nextel

[Alan Clegg]

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

[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_...@isc.org> wrote:
From: Alan Clegg <Alan_...@isc.org>
Subject: Re: Increase max-cache-size
To: pran...@yahoo.com, "DNS BIND" <bind-...@isc.org>
Date: Monday, July 28, 2008, 8:34 PM

[JINMEI Tatuya / 神明達哉]

At Mon, 28 Jul 2008 20:48:28 -0700 (PDT),
Prabhat Rana <pran...@yahoo.com> wrote:

> 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

You can monitor it via the statistics-channel feature (see the ARM).

> 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?

No, reaching the max-cache-size (with an implementation specific
margin) simply triggers LRU-based cache cleaning. named still keeps
caching new data, while purging stale data more aggressively.

---
JINMEI, Tatuya
Internet Systems Consortium, Inc.