The way that RRD works is to 'roll up' data points into averages. If your interval is 5min, then the Daily graph shows you the 1-datapoint averages, the weekly shows you the 6-dp averages, and so on. If you interval is 1-min, then 6-hour is 1dp, and daily is 5dp, and so on. These averages are stored in different RRA datasets (read the RRDTool documentation for the details of how this works)
The practical upshot of this is that the 6hour/daily/weekly/monthly/yearly graphs correspond to the default RRA datasets generated by MRTG, and so they update with a frequency based on the RRA granularity. This means that a daily will always update on 5-min frequency because it will not change more frequently than this due to the nature of RRD. The only thing that will change is the 'last update' time.
routers2 takes advantage of this to cache graphs locally and on the browser in order to minimise work and maximise performance.Statistics: Posted by stevesh — Thu Mar 16, 2006 1:47 am
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