[rrd-users] Re: fetch & resolution

[Matthew Bostwick]

Alex,

Thanks for your help.  I really do appreciate it.  However, I think you
and I were talking about different things.

> There is no such limit.  You really need to RTFM.
> FYI: I'm monitoring something in a 10-second interval, with 40 days
> of history.  That's 350000 rows (40 days times 1440 minutes times
> 6 intervals per minute, rounded up to a nice number).  The same
> amount of rows but for 5-minute intervals would allow for 3 years
> of log...  This is nearly 3 megabytes per DS by the way.

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
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.

[... snip ...]
> > Sample commands & values
> > rrdtool fetch file.rrd AVERAGE --resolution 300 --start 986112000
> > --end
> > 988441200
>
> 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
> 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
> setting.
[... snip ...]

> Some hints:
> Follow the tutorial, even if you don't plan to roll your own.
> Read all about the rrdtool create, fetch and resize commands.
> Start by reading the rrdtool manual page itself.  It is available
> in the doc directory.  If you didn't get the documentation
> (which is a serious error and should be reported!) you can always
> check it on the official rrdtool site.

Thanks for the hints.

> 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:

I re-checked the info in doc/ on rrdtool fetch.  It's almost a match as to
what's one the webpage (I'm running 1.0.33).  Even though I do almost all
of my work exclusively in Unix, I tend to rely on web documentation.  For
instance when I ran into this problem:  I checked all the info on Tobi's
webpage and then I read a ton of the rrd-user list archives.

Anyways, thanks again, you have been pretty instrumental in helping me
write my front-end to rrdtool fetch (I'm not relating directly to the
database).  I'd like to relate directly to the database, but I'm not
quite a perl-wiz yet.  I guess I'm going to have to add another for loop
or two for a day by day print-out.  :-)  Thanks again, Alex.

--Matt


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