[rrd-users] [unsure] Re: Things not adding up
linux at thehobsons.co.uk
Tue Apr 5 22:59:12 CEST 2011
Jared Watkins wrote:
>Ah.. now I think I get it. Put another way... the individual circuit
>maxes aren't occurring at the same moment so you can't simply add those
>max values up and expect to get the total from the stacked values.
>is because (in our case) the circuits are never going to be perfectly
>balanced in traffic volume. This also means the delta between the two
>values is a way of representing the amount of imbalance at the time of
>peak traffic. I don't suppose there would be a way to calculate that
You would have to do it at data collection time, though I appreciate
it might be difficult.
You can do with averaged values, but that may not give you what you
want since the more you consolidate the data, the smoother it tends
to get. My coarsest graphs show one pixel per day over a year, so the
daily variation in traffic flows completely disappears.Where it makes
sense, I have an option to show/hide a max line - and the more the
data is consolidated, the more pronounced the difference between
average and max.
So sticking with just two sources, you would have to modify your
script to collect A and B, and store A+B and a measure of imbalance -
perhaps |(A-B)|/(A+B) which would give the imbalance as a fraction of
the total traffic (min 0 if A=B, max 1 when A=0 or B=0).
You can then consolidate A, B, sum, imbalance, using both average and
max consolidations. You should then be able to graph a stack of A and
B, plus a line for max(sum), and lines for max(imbalance) and
average(imbalance) which I suspect is what you are looking for.
Obviously calculating imbalance gets harder as you add more data sources.
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