[rrd-users] Independent Right Axis

Chris Mason chris at noodles.org.uk
Wed May 9 23:46:16 CEST 2012


I can see this topic has come up before in the archives, but are there
any plans to have an independent right axis which isn't coupled to the
left that rrdtool can auto-scale?

I am trying to plot "bits per second" on the left axis and "packets
per second" on the right axis for the same data.
On a graph I am plotting ifHCInOctets, ifHCInUcastPkts,
ifHCInBroadcastPkts and ifHCInMulticastPkts as well as the outbound

The relationship between "bps" and "pps" isn't always consistent as it
is determined by packet size (i.e. small packets will have a larger
pps rate than larger packets for the same bps). I understand that I
will probably have to have two passes of rrdtool to first fetch the
values before using them in the scale parameters.

Assuming my left axis is scaled automatically then my data could range
from 1 bps to >10 Gbps. If I take some example data then my inbound
"pps" rate is usually a factor of 10,000 times smaller using the
following formula:

(avg bps) / (avg pps) = scale factor

However, if I try the same calculation for outbound traffic then I get
a scale factor of 1,500.

Would anyone who has done something similar be willing to share what
they have done or give me some pointers on the best way to go about

Kind Regards,

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