Recommended value for max-cache-size for cache-only shared hosts..

[Michael Graff]

It's really something you'll have to set, and monitor.  I'd start with 1 GB, and see how close it gets to that in (say) a week.  If it takes a few hours, you might need to go up to 2 or 4, and see how that works.  It may never hit the memory limit.  Also note that there is 10% to 20% overhead, so if you set a 1 GB limit, it's really more like a 1.1GB to 1.2GB limit.  This is because the cache is not the only thing that uses memory, of course, and the limit is only for the cache.

Remember that the cache is only used as a cache, and is not required for operation.  Technically, BIND 9 could run with a very, very small cache.  The default of 32 MB is actually a fairly new thing.  It used to be unlimited, but that means BIND will hit some operating system imposed limit, and that is more painful than self-management.

--Michael

On Jun 1, 2012, at 12:26 AM, blr maani wrote:

> Doug,
>   hmmm.. 75%-85% seems too large because the host runs email application in addition to cache-and-forward-only BIND (for better local caching). So, I was wondering if there are any best/proven practice/recommendations for such shared application hosts ? 
> 
> The default value is 32MB. We have 8GB RAM. I don't know if its better to start with 1GB (1/8th of RAM)?
> 
> thanks
> blr
> 
> 
> On Thu, May 31, 2012 at 8:17 PM, Michael Graff <mgraff at isc.org> wrote:
> Hmm, I don't quite think this is a good idea.  BIND 9 (since 9.5) manages memory quite well, but it will happily consume all you have and go into swap.
> 
> I'd set it high enough (on a dedicated machine) to use plenty of RAM, but low enough to not cause other OS components to swap out or BIND itself to swap.  75% or 85% range seems like a good starting point.
> 
> --Michael
> 
> On May 31, 2012, at 8:18 PM, Doug Barton wrote:
> 
> > On 5/31/2012 1:51 PM, blrmaani wrote:
> >
> >> Question:
> >> what is the recommended configuration for 'max-cache-size' for optimum
> >> usage ?
> >
> > You should not restrict the size of the cache at all if you want the
> > best performance. BIND will use as much memory as it needs in order to
> > satisfy the requests of your users.
> >
> >
> > --
> >    If you're never wrong, you're not trying hard enough
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