[rrd-users] rrd graph not matching figures

Peter Schuller peter.schuller at infidyne.com
Sat Nov 6 16:58:44 MET 2004


Short version: It seems rrdtool is graphing the DEF:s rather than the CDEF:s. 
How can I make it graph the CDEF:s? I want to apply a modifier (in this case 
dividie by 125) to graph bandwidth in kilobits rather than bytes.

Long version:

I've set up rrdtool+snmpd on a couple of hosts now and on both hosts I have 
experienced the same issue. For example, on one host I generate the graph as 
follows (minus some linebreaks added here):

/usr/local/bin/rrdtool graph /usr/local/rrd/www/bw-xl0-60-1h.png -a PNG \
  -h 100  -w 800 -s -3600 -S 60 -v "Data throughput" \    
    "DEF:in=/usr/local/rrd/bw-xl0-60.rrd:in:AVERAGE" \                                                                         
    "DEF:out=/usr/local/rrd/bw-xl0-60.rrd:out:AVERAGE" \                                                                       
    'CDEF:kbin=in,125,/' \                                                                                                     
    'CDEF:kbout=out,125,/' \                                                                                                   
    'AREA:in#00FF00:Bandwidth In'                        
    LINE1:out#0000FF:Bandwidth Out\j' \                           
    'GPRINT:kbin:LAST:Last Bandwidth In\:  %3.2lf KBps'\         
    'GPRINT:kbout:LAST:Last Bandwidth Out\:   %3.2lf KBps\j' \     
    'GPRINT:kbin:AVERAGE:Average Bandwidth In\: %3.2lf KBps' \
    'GPRINT:kbout:AVERAGE:Average Bandwidth Out\:%3.2lf KBps\j' 2>\
    &1 1>/dev/null

The value of the CDEF:s are definitely correct because the numbers printed at 
the bottom by the GRPINT:s are correct. But the graph itself seems to show 
the raw values from the RRD. For example, to test the graph I sustained an 
outgoing transfer rate of about 9.4 mBYTEs/second (according to wget). Now, 
the value of the CDEF ("last bandwidth out") in the resulting graph agrees 
with wget and 'nload xl0', but the graph says "10M" which looks suspiciously 
like the number of octets transfered per second (i.e., about ten million).

How can I tell rrdgraph to graph the CDEF:s rather than the DEF:s, if that's 
the proper terminology?


/ Peter Schuller, InfiDyne Technologies HB

PGP userID: 0xE9758B7D or 'Peter Schuller <peter.schuller at infidyne.com>'
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E-Mail: peter.schuller at infidyne.com Web: http://www.scode.org

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