[rrd-users] 95th and rrd

Andrew Matthews exstatica at gmail.com
Wed Jan 16 02:55:00 CET 2008

I'm semi new to this and i'm a bit confused. What i thought 95th
percentile was, is for 30 days 8640 samples, thats 1 sample every 5
minutes for 30 days, and 5% would be 432. Now the way i understand is
you take all of those samples and lop off the top 5%. leaving what
would become the new base rate.

What i don't understand is in the rrd it only keeps the last few days
of samples before it starts normalizing them across 30 minutes, 2
hours, and daily averages.

This is going by what cacti does. So in a way its not really 95%, its
now a normalized average of over 2 hours with a 95% of that.

Is this how all the software works? Am i missing something? Shouldn't
it be calculated across 8640 samples and not the 2 hour normalized



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