[mrtg] Re: RRDTool and scripts

Kerry Kincaid. kincaid at meer.net
Tue Aug 28 13:32:11 MEST 2001

Tuning the RRD database didn't seem to help.  I tuned the .rrd file, but
MRTG appeared to reset the data source type back to counter and this problem
happened again when the old log file was deleted.  I tried with the original
rateup, and there was no problem.  The graphs look just fine.  Maybe I
should just go back to the original MRTG database.  It seems to have worked
best for my applications in the past.


-----Original Message-----
From: Alex van den Bogaerdt [mailto:alex at slot.hollandcasino.nl]
Sent: Friday, August 24, 2001 8:16 AM
To: kincaid at meer.net
Cc: mrtg at list.ee.ethz.ch
Subject: RD: Re: [mrtg] RRDTool and scripts

Kerry Kincaid. wrote:

> Since there was about 24 days less data to view that the numbers were much
> smaller than usual.  However, this translated into a spike on the graphs
> monster proportions.  I gathered from some of the archived messages that
> Software assumed that the number increased to maxbytes then rolled over to
> zero and continued to go up and calculated the value accordingly.   That
> the wrong thing to do and I'd like to know how I can have it still record
> the data as a counter, but not choke when a log file is deleted.

Proper solution:  front end decides when a wrap occured and when it
did not.  If it did not (so: a reset or so) it sends "U" for unknown
to RRDtool.  Front end in this case is the script that gathers the

Good workaround:
In stead of COUNTER you can use the DERIVE data source type.  When the
minimal tolerable value is set to 0, any wrap or reset will result in
a NaN value generated by the back end.
You can use "rrdtool tune" to alter the DS  *and* the min-value.

 / alex at slot.hollandcasino.nl                  alex at ergens.op.het.net \
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