[rrd-users] Please help me understand this

Simon Hobson linux at thehobsons.co.uk
Fri Oct 15 01:02:31 CEST 2010

Marklar Inc. wrote:
>I really need help understanding this. Im trying to graph five 
>values from 04-10-10 - 08-10-10 which is from Monday to Friday.
>When i do a rrdtool dump, is see the values are correct inserted 
>from Monday to Friday. But when i graph it, it shows from Sunday to 
>One day to early. Im propably doing something wrong.
>The commands are listed below.
>rrdtool create AAPL.rrd --step 86400 --start 1286107200 
>DS:open:GAUGE:86400:0:100000  RRA:LAST:0.5:1:1825
>rrdtool update AAPL.rrd 1286193600:281.60
>rrdtool update AAPL.rrd 1286280000:282.00
>rrdtool update AAPL.rrd 1286366400:289.59
>rrdtool update AAPL.rrd 1286452800:290.34
>rrdtool update AAPL.rrd 1286539200:291.71
>rrdtool graph AAPL.png --start 1286020800 --end  1286576091 --width 
>1600 --watermark "this is wierd" DEF:open=AAPL.rrd:open:LAST 

1286576091 is about half past ten in the evening - so the day is not 
complete and cannot be plotted as a value. The latest whole step 
period ended at midnight (UTC) almost a day earlier.

It's really, really a good idea to use start and end times which 
exactly match the boundaries of the stored data buckets. Also note 
that all times are relative to UTC, so if your timezone is +1, your 
one day periods run from 1am to 1am local time.

Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
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