[rrd-users] New with rrdtool - data is not plotting to graph

[Ben]

Hi,

I am new with rrdtool. I am making a graph for our application which 
provides cumulative data. So for them analysis, I use derive DATA SOURCE 
TYPE. Derive DST means : always take difference from current value and 
last value.


  my rrd command :
     rrdtool create a.rrd \
     --step 60 \
     DS:A:COUNTER:120:0:U \
     RRA:AVERAGE:0.5:1:7200

rrd update command :

     logger rrdtool update a.rrd N:$A
     it shows each time value in syslog, so it is working fine.

rrdtool graph a.png -a PNG \
     --title="Info" -w $Width -h $Height \
     --watermark "`date`" \
     'DEF:A=a.rrd:A:MAX' \
     'LINE:A#00dd00:A' > /dev/null

     it generates blank graph.


     Where i did mistake, please provide your feedback.

     One confusion from me : RRA stands for Round Robin Archive, so when 
we should use MAX/MIN/AVERAGE/LAST with RRA? Please provide some example.

     BR