it turns out a bug in code led to this problem. <br><br>however the "IF.. UN" PRN patch indeed fix another problem caused in-continous boring space(undef+*=undef) in curves.<br><br>thanks a bunch.<br><br><div class="gmail_quote">
On Tue, Jan 5, 2010 at 5:01 PM, Jean-Yves Avenard <span dir="ltr"><<a href="mailto:jyavenard@gmail.com">jyavenard@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Hi<br>
<br>
2010/1/5 George-lll <<a href="mailto:liusoaring@gmail.com">liusoaring@gmail.com</a>>:<br>
<div class="im"><br>
> but if some rrd files have zero/null value(indicate some servers got no<br>
> traffic at that period), the charts combined curve drop to zero too.<br>
<br>
</div>Are they zero or undefined ?<br>
They do not mean the same thing.<br>
<br>
The reason you are seeting what you're describing is because<br>
undefined + anything = undefined..<br>
<br>
If the traffic was 0, you should have added 0 to the RRD via rrdtool<br>
update ; According to your RRD definition, if you do not feed any data<br>
for 2 hours, then entry will be undefined for that period.<br>
<div class="im"><br>
><br>
> wondering there is a data validation before rrdtool starting up, so someone<br>
> let me know hwo to avoid?<br>
<br>
</div>What you could do in your CDEF is something like this:<br>
CDEF:x=val1,UN,0,val1,IF,val2,UN,0,val2,IF,+ etc..<br>
<br>
This will replace all unknown values with 0.<br>
<font color="#888888"><br>
Jean-Yves<br>
</font></blockquote></div><br>