[rrd-users] wrong rra used

spock collector at sappers.de
Thu Jun 26 16:01:11 CEST 2014

Hello Simon,

thanks for your comments...

> It does the best it can to use the most detailed data. Looking at the
> docs, I don't see any
> option to override that. 

I saw a similar setup on  Link <http://www.kompf.de/weather/technik.html > 
and there are also a 2 RRA; the example graph showed the correct average
line: average of all values of a single day.
Maybe I try to contact him if there is any "trick" involved.

Do you see any trick to create a single data point per day with the average
value (temperature)?

> Looks more like an hour to me, are you on +1 timezone by any chance ? 
Yes, I am in UTC+1 timezone...
So data consolidation is always done based on UTC+0 timezone.

I am using the following unix statements to get the timestamp:

        set $(date "+%Y %m %d %H %M")
        timestamp_rounded="$1$2$3 $4:${m#1}"
        timestamp_rounded_unix=$(date --date "$1$2$3 $4:${m#1}" +%s)
        timestamp_real=$(date "+%Y%m%d %H:%M")
        timestamp_real_unix=$(date --date "$timestamp_real" +%s)

If I check my own logfiles, i can see:
I106 rrdtool update /testtemp/temp_pool.rrd
I103 20140625 15:15 --> this is my time, UTC+1 CEST

1403702100 translates into 25.06.2014 - 15:15:00

So the algorithm from a rrdtool perspective uses my time as UTC+0 time.

I still cannot explain this 1h offset in the graph...

> Are you certain you are updating frequently enough ? 

The reason here was a downtime due to maintenance work.
Well, as I understand it, the RRA function tolerates with SSF 0.5, that 50%
of data points may be missing. As you can see in the graph, there are a few
values missing, but not 50% (48 data points out of 96).  Or does the max
function return no values, if the data vector contains unknowns?

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