[rrd-users] Can't I turn off data smoothing for GAUGE?

Marc MERLIN marc_rrd at merlins.org
Tue Aug 17 08:02:51 CEST 2010


I had a problem, which is explained in more details here:

Basically, I use a GAUGE as a bitfield because I don't have anymore room
to add DS entries in my RRD since it's already 2GB.

I've been told that rrdtool does not allow turning off data smoothing,
even for GAUGE.  Is that true?
If so, can this be considered as a feature, there are definitely causes,
even if you don't abuse a GAUGE DS as a bitfield, where smoothing data
would just yield total rubish data that shouldn't be there by creating intermediate
values that may not be valid data at all.


The original question on the cacti forum was:
I'm using a data source as a bit field to keep track of fan or HVAC status in my house.
bit 1: hvac heat, bit 2: hvac cool, bit 7: computer fan closet on.

So my raw data looks like 129, 128, 2, 0 and so forth.

Unfortunately when I go from 128 to 0, rrdtool tries to be helpful and smoothens my data, so I end up with intermediate values like 66.13:

Can I tell cacti/rrdtool to jump from 128 to 0 and not smoothen values?

For now, I get garbage like this:
(the lines in the graphs are due to the induced error above).

If you're curious, I use this CDEF for each bit I want to display:

When things actually work (here it's bit 7, 128 so I don't get the average rouding bug), here's what it looks like:

"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems & security ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/

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