[rrd-users] Re: New, need some clarification on creating and inputting

[Alex van den Bogaerdt]

On Tue, May 25, 2004 at 02:17:20PM -0700, Joseph Oaks wrote:

> I have a need to graph the iostat on a number of boxes. So I have 
> create a rrd file to track 4 of the fields, rkB/s, wkB/s, await, 
> and %util.

The choice of GAUGE is a good one probably.

>            I understand that I will need a seperate rrd file for
> each partition, /dev/hda, /dev/hda1, etc... So this is what I came
> up with...

You do not _need_ a separate rrd file.  IMHO it _is_ a good choice
to have separate files, just in case you are going to add another
disk.

> rrdtool create \
> localhost_iostat_hda.rrd \
> --step 300 \
> DS:hda_read:GAUGE:600:0:U \
> DS:hda_write:GAUGE:600:0:U \
> DS:hda_await:GAUGE:600:0:U \
> DS:hda_percent:GAUGE:600:0:U \
> RRA:AVERAGE:0.5:1:600 \
> RRA:AVERAGE:0.5:6:700 \
> RRA:AVERAGE:0.5:24:775 \
> RRA:AVERAGE:0.5:288:797 \
> RRA:MAX:0.5:1:600 \
> RRA:MAX:0.5:6:700 \
> RRA:MAX:0.5:24:775

No problems, except that I wonder why you won't have a MAX RRA with
steps==288.  This is not an error; it may be an unfortunate choice.

> When I have attempted to add these four entries manually it seems
> to work just fine doing...
> rrdtool update localhost_iostat_hda.rrd N:62.07:36.09:27.14:101.02

Looking good.  You don't say there are, so there are no errors when
you run this script.  Just to be sure, you _did_ run it multiple times
with approximately 5 minutes inbetween?

> Yet when I try to fetch I get the following...
> [root at joaks scripts]# rrdtool fetch localhost_iostat_hda.rrd AVERAGE -r 300 -s -1h
>                        hda_read            hda_write            hda_await    hda_percent

[snip]
> 1085518500: nan nan nan nan
> 1085518800: nan nan nan nan
> 1085519100: nan nan nan nan

When was your last update.  What does rrdtool info tell you.

For debugging: create a script containing a couple of updates,
with explicit timestamps, and query the database.  For instance:

 rrdtool create ...[and so on]...
 rrdtool update localhost_iostat_hda.rrd 1085518500:62.07:36.09:27.14:101.02
 rrdtool update localhost_iostat_hda.rrd 1085518800:62.07:36.09:27.14:101.02
 rrdtool update localhost_iostat_hda.rrd 1085519100:62.07:36.09:27.14:101.02
 rrdtool fetch localhost_iostat_hda.rrd AVERAGE -r 300 -s -1h -e 1085519100

If necessary, use rrdtool dump and look at the resulting xml file.

Maybe this will gave you some pointers to find your problem.
HTH
Alex
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