Hi Chris, On Tue, 2013-08-06 at 08:20 -0700, Chris Mason wrote: > Hi Jonan, > > > > But when looking at a year, you may have consolidated the > individual numbers into larger buckets - where the max-values > are kept. > Lets just create an example where two values are > "joined" (timeslot increased to contain 2 values) - so we > reduce the buckets to 5. > 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). > > With the same max, we would then have: > > 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 > > Where the max-value is 13 - and not 12 as above. > > > > I see what you are saying, but this would change the MAX of A2 and MAX > of B2 between different bucket sizes. > 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? > > > i.e. > > > 1M MAX of A: 749.807 M > 1Y MAX of A: 749.807 M > > > 1M MAX of B: 1744.822 M > > 1Y MAX of B: 1744.822 M
Even if data is consolidated - you will get the max-values - as your RRD's are set up to keep these. But looking on a wider scope - you may get a difference on the sum of the Max - I think... :-) Another example. of single samples. A: 1 2 3 3 2 1 B: 3 2 1 1 2 3 For each of the above - the sum is always 4 - when adding up A and B numbers. 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. The sum of these are 6 - (and not 4). So if larger buckets are created - and the sum of these are calculated you will end up with a higher number. For network bandwidth it's normal to look at the 95%-percentile. At work we do store 5 years of 5-minute data without consolidation. 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). When exporting data, I think that it's possible to control this bucket-consolidation. I'm not sure how to tackle your problem, but I would still think twice before using MAX. /Johan > > I'm not sure what you want to accomplish. > 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. > > > > 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. > > > Regards, > Chris
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