[rrd-users] Re: start time

Alex van den Bogaerdt alex at slot.hollandcasino.nl
Thu Jun 21 22:43:48 MEST 2001

Joseph E. Eggleston wrote:
> I don't necessarily have data that starts in 1970, but I don't know the
> exact time that the data will be starting. It seemed better to not have
> rrd check. The question really is, why does rrd care when the start time
> is?

It just needs to know.  The database is "steps" * "rows" intervals of
"step size" seconds, starting at "start time".  If you leave out the
start time, it will default to "now" minus "steps" * "step size" * "rows".

If you try and specify 0 as the start time and have, for instance, 600
rows of 300 seconds each, you are defining a database that covers
januari 1st 1970, 00:00 UTC to januari 3rd 1970, 02:00 UTC.

If you then start entering data at, for instance, june 21st, 00:00 UTC
it takes a very long time for RRDtool to catch up.  It needs to recalculate
every single interval ("step size" * "rows").

>     I've tried putting in other low numbers, such as 1, and still get the
> same error. I guess I am trying to figure out if there is a more limited
> range of dates that rrd can handle.

There is.  From the source:
      if (last_up < 3600*24*365*10){
         rrd_set_error("the first entry to the RRD should be after 1980")

This probably has been put in there because of the problem I described
above.  If people don't understand what's going on and are able to enter
things like 20010621 (probably because they ment june 21st, 2001) much
more confusion will happen.

 / alex at slot.hollandcasino.nl                  alex at ergens.op.het.net \
| work                                                         private |
| My employer is capable of speaking therefore I speak only for myself |
| Technical questions sent directly to me will be nuked. Use the list. | 
| http://faq.mrtg.org/                                                 |
| http://rrdtool.eu.org  --> tutorial                                  |

Unsubscribe mailto:rrd-users-request at list.ee.ethz.ch?subject=unsubscribe
Help        mailto:rrd-users-request at list.ee.ethz.ch?subject=help
Archive     http://www.ee.ethz.ch/~slist/rrd-users
WebAdmin    http://www.ee.ethz.ch/~slist/lsg2.cgi

More information about the rrd-users mailing list