This means that when you have a measurement that changes suddenly, then the data stored in the RRD file tends to lag behind slightly (for 10 thanks, Henrik. To get some dynamic data quickly, I used $((RANDOM%100)) which jumps up and down like crazy. If RRDTOOL store averages only, that makes perfect sense.
On 1/16/07, Henrik Stoerner <henrik at hswn.dk> wrote:
The way RRD files work means that they will practically NEVER store the exact value you push into them. Whenever you update an RRD file with a new measurement, it looks at how long time has passed since the previous update, and then computes what the new value "should" be, if the update had occurred at exactly 300 seconds interval.
This means that when you have a measurement that changes suddenly, then the data stored in the RRD file tends to lag behind slightly (for 10 minutes or so).
Hobbit feeds the percent-used measurement into the RRD files, and rrdtool takes care of all the data manipulation needed to create graphs from the data. BUT - Hobbit looks at the measurements BEFORE sending them through rrdtool. So Hobbit will trigger an alert as soon as the measurement says "97% used", regardless of what data the RRD-file has as the CUR value.
Regards, Henrik
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