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Hi Chris,<BR>
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On Tue, 2013-08-06 at 08:20 -0700, Chris Mason wrote:
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Hi Jonan,
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But when looking at a year, you may have consolidated the individual numbers into larger buckets - where the max-values are kept.<BR>
Lets just create an example where two values are "joined" (timeslot increased to contain 2 values) - so we reduce the buckets to 5.<BR>
Most people have maybe 2 weeks of data with full resolution, and then consolidate this to larger buckets (from minutes to hours) - and then after a few months of them - go up to some even larger buckets (hours to days).<BR>
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With the same max, we would then have:
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A2: 3 5 6 4 4
B2: 6 8 4 3 1
And our new max-array of the sum would be:
AB2: 9 13 10 7 5
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Where the max-value is 13 - and not 12 as above.<BR>
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I see what you are saying, but this would change the MAX of A2 and MAX of B2 between different bucket sizes.
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But, if A and B both return the same MAX value for a 1 year resolution and a 1 month resolution graph then doesn't this imply they aren't being reduced?
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i.e.
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1M MAX of A: 749.807 M
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1Y MAX of A: 749.807 M
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1M MAX of B: 1744.822 M<BR>
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1Y MAX of B: 1744.822 M
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Even if data is consolidated - you will get the max-values - as your RRD's are set up to keep these.<BR>
But looking on a wider scope - you may get a difference on the sum of the Max - I think... <IMG SRC="cid:1375817424.3013.102.camel@cph-drift2.eur.adobe.com" ALIGN="middle" ALT=":-)" BORDER="0"><BR>
Another example. of single samples.<BR>
A: 1 2 3 3 2 1<BR>
B: 3 2 1 1 2 3<BR>
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For each of the above - the sum is always 4 - when adding up A and B numbers.<BR>
But when all the 6 values are consolidated to a single value - and you use MAX - you will end up having 3 for A - and 3 for B.<BR>
The sum of these are 6 - (and not 4).<BR>
So if larger buckets are created - and the sum of these are calculated you will end up with a higher number.<BR>
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For network bandwidth it's normal to look at the 95%-percentile.<BR>
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At work we do store 5 years of 5-minute data without consolidation.<BR>
RRD do however create larger buckets anyway - especially when output is a graph - as all the 525600 samples can't fit in a graph anyway. (when looking at 5 years).<BR>
When exporting data, I think that it's possible to control this bucket-consolidation.<BR>
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I'm not sure how to tackle your problem, but I would still think twice before using MAX.<BR>
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/Johan <BR>
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I'm not sure what you want to accomplish.<BR>
If you are trying to look on some bandwidth-numbers you should probably not use max anyway - as even a very short peak would offset your hole yearly-data.<BR>
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I am measuring link utilisation and we graph MAX as opposed to AVERAGE as this gives us more accurate information on peak utilisation. They are generally very high capacity links which don't produce bursty graphs.
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Regards,
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Chris
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