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

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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