[rrd-users] Re: Problems with multi-DS RRD that gets asynchronous-DS updates

[Alex van den Bogaerdt]

> A collection script runs every 5 minutes.  It did:
> 
>   rrdtool update MadisonSD.rrd 937503600:475724299:104956107
> 
> Then at 1999-09-16 12:45:00 CDT, it did snmpgets across
> a second boundary so my script stuffed values into rrd via:
> 
>   rrdtool update MadisonSD.rrd -t input 937503900:496053104
>   rrdtool update MadisonSD.rrd -t output 937503901:108120595
> 
> I expect the value of the DS output at 1999-09-16 12:45:00 CDT to be
> 1.058e+04 = (108120595 - 104956107) / 300.
> 

(108120595 - 104956107) / 301 to be exact.

> But instead I get NaN:
> 
>   <!-- 1999-09-16 12:45:00 CDT --> <row><v> 6.7762683333e+04 </v> \
>     <v> NaN </v></row>

This means that your RRD doesn't allow for updates more than 300
seconds apart. Check your heartbeat settings, I bet they are 300.

> 
> So about 1/10th of my data values are "NaN" and thus a
> last-four-hour graph looks pretty bad because 1/10th of the
> LINEs and AREAs are at zero. =:(
> 

technically no, they are unknown which is completely different from
zero.


HTH,
Alex

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