How to calculate Buffer Hits Ratio

Posted by gamerome on 10-Dec-2013 10:36


How can I calculate using VST the buffer hits ratio, we can see via promon?

I don't know which VST and fields to use...


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Posted by gus on 10-Dec-2013 14:55

The computation done by the promon program for the buffer hit ratio is

(logical reads + logical writes - os reads) * 100


(logical reads + logical writes)

these values can be obtained from a couple of places in the vsts. Using _actbuffer, the hit ratio is

hr = ((_buffer-logicrds + _buffer-logicwrts - _buffer-osrds) * 100) / (_buffer-logicrds + _buffer-logicwrts).

note that small differences in the hit ratio can mean much larger changes in the i/o rate. for example, a decrease in the hit ratio from 99.5  to 99.0 percent is double the i/o.

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