[hobbit] why rrd/do_disk.c couldn't store/extract correct CUR value to RRD?

[Jerry Yu]

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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>
>
>
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