[rrd-users] Re: rrd updates give NaN

[Frank D. Gunseor]

Please excuse me if I am butting in, but I have been following this thread
with great interest.

I am just starting out with RRD and I am having a very similar problem.

Here is the way I created my database in Perl v 5.8.8:

# if the database hasn't been created,
# do so now, or die with an error.
#print "Creating database!";
if (!-f $db) {
    RRDs::create ($db, "--start", $now-1,
          "DS:IBM:ABSOLUTE:900:0:U",
          "DS:MSFT:ABSOLUTE:900:0:U",
          "DS:LNUX:ABSOLUTE:900:0:U",
          "RRA:AVERAGE:0.5:1:4800",
          "RRA:AVERAGE:0.5:4:4800",
          "RRA:AVERAGE:0.5:24:3000",
    );

    if (my $ERROR = RRDs::error) { die "$ERROR\n";}
} 

When I look at the database with RRD Editor or with fetch I see a lot of
Nans.

Does RRD "back populate" the database with NaNs to be able to creat the
averages when it is first created???

I am using a perl program crontab to collect the data every 15 minutes. I
checks every minutes and runs the perl program starting on the hour, 15
minutes after, 30 minutes after, 45 minutes after, etc.

I would appreciate any help and or insight so I could learn more and correct
my mistakes.

Thank you.

Frank

-----Original Message-----
From: rrd-users-bounce at list.ee.ethz.ch
[mailto:rrd-users-bounce at list.ee.ethz.ch] On Behalf Of Tony Howat
Sent: Monday, July 31, 2006 11:09 AM
To: alex at ergens.op.het.net; rrd-users at list.ee.ethz.ch
Subject: [rrd-users] Re: rrd updates give NaN

Alex van den Bogaerdt wrote:

>What you are saying is like this in pseudo code:
>
> > while forever
> > do
> >     run_rrdtool
> >     sleep 60
> > done
>
>The execution time of this loop is more than 60 seconds.  Say it takes 
>0.1 seconds to 'run_rrdtool'.  If you require the updates to be no 
>further apart than 60 seconds, and if you update every 60.1 seconds, 
>each update will arrive too late.
>
>I'm not saying this has to be the cause of your problem.  I do say 
>something like this is the most likely cause.
>
>
>Try changing that 'N' into a real timestamp and then log every update 
>command so you can do some analysis.

Feeding time() values in instead of N seems to have done the trick.

Many thanks for your help!

--
Tony


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