[rrd-users] Timestamp problem

Alex van den Bogaerdt alex at vandenbogaerdt.nl
Tue Feb 24 13:20:50 CET 2009

> So, it looks to me like rrdtool uses UTC time which is lagging my local
> time by one hour (as expected). Do I have to bother about that one hour?

You should worry if it didn't. That would mean there's something wrong with 
the clock or timezone on your computer.

During daylight saving the difference has to be 2 hours.

> The reason for me to start looking into this was that all of a sudden I
> could not get reasonable results out of my databases.
> In the three first printouts below you could see what I get when I use
> the "info" functionality in rrdtool. I get values that seem reasonable
> (temperature, humidity and dew point in my cellar), but when using fetch
> to try to get the average value (over 10 minutes) I always get the same
> out of the database. The values you see in the last printout below are
> the same as I got 24 hours earlier as well as some 48 hours earlier.

The timestamps say today at 08:10 local time. If you did in fact get exactly 
the same information 24 hours ago and 48 hours ago then:

a: you updated the database some time ago with a wrong timestamp, either 
because you specified a time or because your clock was set wrong when using 
b: you should look at the error messages which rrdtool gives you.

No, "rrdtool update ....   1>/dev/null 2>&1" is not a smart thing to have in 
your crontab.

If that wrong timestamp is not the problem, well, then I say the information 
you showed looks OK to me. Unless you explain what is wrong, how it should 
look according to you, why and so on, it will be hard to help. Throwing some 
numbers in an email and saying they're wrong, is wrong.

Before you post back, have a look at the process yourself. I bet it still 
works as expected, and you are only confused because RRDtool is _not_ what 
you get out is what you put in. And that's by design. It is also explained 
on my site, under "Rates, normalizing and consolidating".

Please go to the index page: http://www.vandenbogaerdt.nl/rrdtool/ 

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