To understand what these areas mean, you need to understand how rrdtool works. RRD "aggregates" data over time. For example, our RRDs might store :

1 day of 5-min resolution data 7 days of 15-min resolution data 30 days of 1 hour resolution data 2 years of 1 day resolution data

For each of these datapoint it stores minimum value, maximum value and average value.

If for example I had these datapoints :

1:00 - 25 1:05 - 26 1:10 - 24 1:15 - 25 1:20 - 25 1:25 - 25

If we're showing a graph of the last day's data, we'll see this as a red line. If we're seeing this data in a graph containing data from the last 7 days the datapoints above would be aggregated into :

Avg Min Max 1:00 - 25 - 24 - 26 1:15 - 25 - 25 - 25

You'd see a red line at 25 as both datapoints would have 25 as average.

This can give a false impression sometimes, especially with things like sensors, so we also plot the min/max value range too as the grey area.

Depending upon the time period, the min/max values might be more important than the averaged line, depending what data you want.

adam.

On 2014-09-24 17:34, Zhenhui Liang wrote:

Thanks so much. That explains.

From: Joel Krauska <jkrauska@gmail.commailto:jkrauska@gmail.com> Date: Wednesday, September 24, 2014 at 9:29 AM To: Observium Network Observation System <observium@observium.orgmailto:observium@observium.org> Cc: Zhenhui Liang <ZhenhuiLiang@eharmony.commailto:ZhenhuiLiang@eharmony.com> Subject: Re: [Observium] graph color

I believe the red line shows your actual data points. (keep in mind that RRDs self average over time) I believe the grey area implies variance [1].

Smokeping uses this as well. http://oss.oetiker.ch/smokeping/doc/reading.en.html

1. http://en.wikipedia.org/wiki/Variance

On Wed, Sep 24, 2014 at 8:45 AM, Zhenhui Liang <ZhenhuiLiang@eharmony.commailto:ZhenhuiLiang@eharmony.com> wrote: Guys,

This might be a general RRD question. So in almost all graphing, we have those shaded color area and solid color line. Although I have a general idea on what they mean, I still want some official explanations regarding their meanings. Thanks.

I attached a cpu usage graph here as an example. We have grey shaded area, and solid red line.

I guess the red line is some kind of moving average? While grey shows spikes? Or how else could I inteprete this?

Thanks a lot.

Zhenhui[cid:2CB03DFE-FFA0-4DA8-9438-EB2732F92119]

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