Re: a question about hit rati

From: Alex Rousskov (rousskov@measurement-factory.com)
Date: Tue May 21 2002 - 22:46:35 MDT


On Wed, 22 May 2002 chin60@pchome.com.tw wrote:

> Our proxy server is based on polymix-3.pg and
> polygraph-2.5.4. We find the larger peak request rate is,
> the less hit ratio occurs. For example, our cache disk is 35GB
> peak request rate 200 => hit ratio 57%
> peak request rate 400 => hit ratio 49%
>
> And the response time of the two test results are OK, both under
> 2800 msec. Could someone tell us the reasons? thanks!

There may be several reasons, including the following:

        - higher peak rate means larger working set size;
          you proxy may need larger cache to keep more
          objects that could be revisited

        - some proxies serve fewer hits to reduce disk
          bottleneck under overload conditions

Also, please note that a "good" mean response time for PolyMix-3
should be below 2 seconds (2.8sec is good for misses only; hits should
be much faster). Perhaps you were quoting miss response time
statistics though; ignore this paragraph in that case.

Alex.



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