[rrd-users] Re: problem with data shown in rrd

Sat Sep 7 14:58:18 MEST 2002

On Sat, Sep 07, 2002 at 12:25:52AM -0500, Bruce Alexander wrote:
> 
> Hello everyone,
> 
> I apologize in advance for my newbieness with RRDtool, but I have wrestled
> with this problem for over 2 weeks and have come up with no solution.  Nor
> have I seen anything like this mentioned in the mailing list archives.  I
> will say that RRDtool looks quite awesome still despite my headaches though,
> which are probably induced by some little thing I missed in the manuals.

?

It seems you do the right thing as far as RRDtool is concerned.
Therefore we may assume the manuals are OK.

[snip perl script for getting ifInOctets and ifOutOctets]

You don't check for errors.  First of all, start by writing
your RRDtool command to a log file for future reference. This
makes it possible for you to debug the script and/or your setup.

Perhaps it becomes clear what the problem is when you see things
like "rrdtool update N:-1:-1" (for instance) in your debug file.
Also, this enables you to compute by hand what any update would
result into.  Compare this to the rates reported in a dump.

> rrdtool create somerrd.rrd DS:input:COUNTER:600:U:U
> DS:output:COUNTER:600:U:U RRA:AVERAGE:0.5:1:600 RRA:AVERAGE:0.5:6:700
> RRA:AVERAGE:0.5:24:775
> RRA:AVERAGE:0.5:288:797 RRA:MAX:0.5:1:600 RRA:MAX:0.5:6:700
> RRA:MAX:0.5:24:775 RRA:MAX:0.5:288:797

You didn't set limits on the counter.  So, if you update with
counter value 1 and next time update with counter value 0 (due
to a buggy script, a router reset or whatever other reason) the
increase will be 2^64-1 and the rate becomes (2^64-1)/300.

That is a typical example of what you're seeing, in its most
extreme case.

> rrdtool graph somerrd.gif --start -86400
> DEF:inoctets=somerrd.rrd:input:AVERAGE
> DEF:outoctets=somerrd.rrd:output:AVERAGE AREA:inoctets#00FF00:"In traffic"
> LINE1:outoctets#0000FF:"Out traffic"

Unless you're running an old version of RRDtool, the resulting
picture will be PNG, not GIF.

HTH
Alex

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