[rrd-users] rrd starting at a certain date

[Stefan M. Brandl]

On Tue, Apr 13, 2010 at 09:20:23AM +0100, Simon Hobson wrote:
> Stefan M. Brandl wrote:
> >Hi there,
> >I want to create a rrd-database starting at Friday Feb. 26 2010 and have
> >a step of one week.
> >If I do
> >
> >rrdtool create test.rrd --start 1267056000 --step 604800 
> >DS:test:GAUGE:604800:0:U RRA:AVERAGE:0.5:1:100
> >
> >the resulting rrd starts at Thursday Feb. 25.
> >Regardless how I set the start-date, it is always set to Thursday.
> >What am I doing wrong here?
> 

First of all, the above example is wrong.
--start should be 1267142400.

> Timezone ?
>

Seems not to be the problem.
If I set the start-date 3600 seconds higher or 3600 seconds lower,
the result is always the same. Startdate is always set to 1267056000 (look
in the resulting rrd-dump).
 
> Your email says +2 (European summer time ?), so midnight by your 
> clock is 22:00 UTC. RRCTool only uses UTC.
> 
> In any case, the start time in an RRD file is largely irrelevant. 

Why?
I want a 1 week interval with data inserted every friday.

> Once you've done a single update, then that will set the minimum time 
> for a future update, and the start time of each consolidated data set 
> will be determined by the step time, number of PDPs per CDP, and the 
> number of CDPs to keep.
> 

Yes, this should be correct, but I always ad the data at a friday.
If I dump the database, it look like I have stored the data 24h earlier,
this is not nice.


Stefan