[rrd-users] Unexpected value in RRD

[Karl Fischer]

Am 15.06.2010 13:57, schrieb Rajkumar S:
> Hi all,
> 
> I was debugging a wrong graph in cacti and it finally boiled down to
> wrong value in RRD.
> 
> To debug I have isolated the problem into simple rrd commands, while
> my input data is correct, the actual value stored in RRD is not what I
> expect. I am not really sure what is going wrong!
> 
> I am creating RRD using the following command:
> 
> /usr/bin/rrdtool create \
> test1.rrd \
> --start 1276487400 \
> --step 300  \
> DS:value1:COUNTER:600:0:12500000 \
> RRA:AVERAGE:0.5:1:600
> 
> I insert the following values into it:
> rrdtool updatev test1.rrd 1276487402:3179452 1276487701:3179779 \
> 1276488001:3180113 1276488302:3180441 1276488601:3180768 \
> 1276488902:3181106 1276489201:3181450 1276489502:3181804 \
> 1276489801:3182186 1276490101:3182505 1276490401:3182828
> 
> I get the following output:
> 
> return_value = 0
> [1276487700]RRA[AVERAGE][1]DS[value1] = 1.0936454849e+00
> [1276488000]RRA[AVERAGE][1]DS[value1] = 1.1132677072e+00
> [1276488300]RRA[AVERAGE][1]DS[value1] = 1.0897797711e+00
> [1276488600]RRA[AVERAGE][1]DS[value1] = 1.0936191884e+00
> [1276488900]RRA[AVERAGE][1]DS[value1] = 1.1228259944e+00
> [1276489200]RRA[AVERAGE][1]DS[value1] = 1.1503178183e+00
> [1276489500]RRA[AVERAGE][1]DS[value1] = 1.1759944740e+00
> [1276489800]RRA[AVERAGE][1]DS[value1] = 1.2769152250e+00
> [1276490100]RRA[AVERAGE][1]DS[value1] = 1.0640475288e+00
> [1276490400]RRA[AVERAGE][1]DS[value1] = 1.0766222222e+00
> 
> The difference between two values inserted is around 300 and time
> difference is 5 minutes. I expected the values to be 327, 334, 328,
> 327, 338 etc... but the values  that is inserted into RRD is around 1
> as you can see from the output above. I am using  RRDtool version
> 1.3.1 in debian.
> 
> Any help to find out what is wrong is greatly appreciated.
> 
> Thanks and regards,
> 
> raj

Hi Rajkumar,

you are using COUNTER as the DS-type, so the values are normalized to 1/s.
So to get a value for 300s you have to multiply it by 300.

eg. 1.0936454849e+00 * 300 = 328.09364547

The remaining difference comes from not inserting at the top of the interval.

You've been using 1276488001 instead of 1276488000, 1276488302 instead of
1276488300 and so on ...


hth

- Karl