[rrd-users] Re: disabling units on vertical axis

Alex van den Bogaerdt alex at slot.hollandcasino.nl
Tue Dec 25 14:17:02 MET 2001

Anant Tamgole wrote:

> We are trying to graph crc errors, carrier transitions, input/output queue
> drops for cisco routers.
> I am getting units on vertical axis as 10m, 20m, 30m OR
> sometimes 10M, 20M. 
> So, what does m stands for and why I am getting M, when carrier
> transitions etc. are hardly 1 or 2 per second.

m is mili, M is mega.  If you have one error during an interval of 300
seconds, there are *on* *average* 1/300 errors per second during the
*whole* interval. This is (close to) 0.0033333 errors per second or
3.33 mErrors.  For more information see the faq pages.

If you reset the counters (perhaps by rebooting the device), you will
have a counter that goes from (for instance) 10 to 0.  The difference
is then (new-old) = (0-10) = (-10).  The counter wrapped according to
RRDtool so the difference is 2^32 more.  This is 4294967296-10 is
4294967286.  This difference divided by 300 is 14316557 per second,
or 14.316557 MErrors per second.

This is not RRDtool doing things wrong, it is the front end that
has to make sure to send correct data to rrdtool.  The user, that's
you, should also set minimum and maximum acceptable rates in the
DS (you have U:U).

Try to detect a reboot.  If it happens, insert an unknown value in the
data input.  Numbers will be 10,U,0 in stead of 10,0 and you will not
have a problem. Setting the maximum to 2,000,000 or so will also help,
you'd have to get 2 million errors per second to get into trouble.

Last but not least: if you have this kind of counter it is highly
unlikely that there will ever be a valid wrap of the counter.  In
that case you can use the DERIVE type in stead of COUNTER.  Derive
can go up and down (so: 10,0 would result in -10/300, not in 14M),
but you can set the minimum allowed value to 0.  -10/100 will then
be discarded (setting the unknown for you).  This is not a smart
thing to do when you're graphing a 100Mbps interface's counters!

> Or can we completely disable this labeling on vertical axis.   

Then what?  You have a line that goes up and down, without knowing
the numbers.  You will only see the problematic peaks (the 14M).
This won't help you I'm afraid.

Merry Christmast and a good MMII to you all!
 / alex at slot.hollandcasino.nl                  alex at ergens.op.het.net \
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