[mrtg] Re: Log file and graph not the same.

Peter Glanville peter_glanville at cuk.canon.co.uk
Tue Jun 8 11:35:04 MEST 2004


> I have a problem and I am not sure where to look. I was thinking it had 
to
> do with Options: but now I am not sure.
You have two seperate issues

> I am graphing my network print spooler. The number above each MRTG log 
is my
> spooler as I see it and in my cfg file I muylitple it by 300 because my
> understanding is that if you do not use "gauge" then MRTG treats 
variables
> as a counters and calculates the difference between the current and the
> previous value and divides that by the elapsed time between the last two
> readings to get the value to be plotted. "from the doc". Any ideas what 
I am
> seeing? Is it normal? -- Look for the (???) (all polls are 5 minutes)

You do not want 'gauge', as you are reading a counter.
Your problem is that the default option is to calculate the rate of 
increase 'per second'. In your case that is below one, and it plots a 
zero.
You have actual readings of 4 or 5 every 5 mins, so you might want to use 
the 'per minute' or 'per hour' options
Multiplying by 300 gives you a 'per 5 mins' reading, which may be mildly 
confusing for some users to understand.

Your second issue (the graph is not quite what you expect) is down to 
'normalisation'
If the counter increases by 1500 during one interval, 50 in the next and 
20 in the third, the chances are that during the middle interval you did 
not do exactly 50 for the whole time, but started high (as per the 
previous interval) for a brief while and swooped down. So during most of 
the second interval, you were at a lower level than the average rate. So 
the graph roughs out a more likely curve. 
This does cause frustration (and a number of emails to this mailing list) 
especially when graphing a Gauge. But the overall effect is about right, 
so live with it.

Peter




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