[rrd-users] Re: fetch & resolution

Matthew Bostwick mattb at hive.54.org
Sun Apr 29 12:08:19 MEST 2001

On Sun, 29 Apr 2001, Alex van den Bogaerdt wrote:

> Matthew Bostwick wrote:
> >
> >
> > However, I think you and I were talking about different things.
> no we're not.  There is no such limit.
> > I was refering to the rrdtool fetch program not as to the database
> > limitations.  After reading your above comments, it seems pretty
> > clear that there are fetch limitations.  If there weren't
> There is no such limit.  There probably is *some* limit but it is
> not anywhere near 600 rows.
> > limitations, the fetch commands bellow would work, right?  Here's a snip
> > of some stuff we talked about before...  I was talking about the same
> > subject.
> >
> > > You try to fetch (988441200-986112000)/300 = 7764 rows.  How many rows
> > > does your database have for the 5-minute RRA ?  Suppose you only have
> How many rows does your database have for the 5-minute RRA ?   600?
> If you have only 600 rows, *you* *cannot* *fetch* *more* *rows*.
> > > 600 rows (the default if you use MRTG-like RRDs), you can only ask for
> > > 600*300 = 180000 seconds worth of data in a 300-second resolution.
> > > Any more and RRDtool will automatically override your resolution
> You can only query if it's in the database.  If it is not in the
> desired RRA, the RRDtool programs (including but not limited to fetch)
> will use another RRA.  This *is* what's happening to you.  This is
> not a fetch problem, it is no problem at all.  The limitation is in
> the database itself.  Not in the program, in the database.  This is
> user defined.
> > > No offence, but creating yet another webpage which isn't read anyway
> > > is the last thing I'm going to do.  From the rrdtool manual page:
> And this is where I get lost.  The snippet I included talked about
> just what you don't understand.  You deleted it ?!?

Hey Alex!

Thanks for spending some time today with me.   Here's that snipit of logic
you sent earlier.

    "It works like this: If you want to store 1000 values
     in 5 minute interval, rrdtool will allocate space
     for 1000 data values and a header area."
    "This automatically limits the history to the last 1000 values."

Okay, here's a dumb question.  How do I figure out how many rows there
are in a give rrd data file?  It doesn't seem like I can dump by row, but
just by date.  Heck I'd dump all and stick it into an array, if I could do

Thanks for helping me out.  I guess I was clueless all along while writing
up everything.


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