[rrd-users] Re: Newbie help need

David Edward Shapiro David.Edward.Shapiro at btitele.com
Tue Nov 20 14:49:47 MET 2001

Thanks a million for responding.  I put a few questions in below:
-----Original Message-----
From: Serge Maandag [mailto:serge.maandag at staff.zeelandnet.nl]
Sent: Tuesday, November 20, 2001 4:07 AM
To: David Edward Shapiro; rrd-users at list.ee.ethz.ch
Subject: RE: [rrd-users] Newbie help need 

The seconds you're graphing are GAUGEs. 

Think of the difference between conters and gauges as this: 

To measure intervals you could use an ordinary clock. 
The output would be something like: 

09:00:00 start 
09:02:30 interval 1 
09:05:30 interval 2 

To graph that you'd probably want a graph that plots the intervals, in this
case 150 and 180 secs. That's what the counter option is for. It subtracts
the value measured before from the value measured now and stores the

In your case you already have interval values. They need no processing
anymore, so they're gauges.

As for the averages: They determine the resolution of your data. rrd's are
made for storing data that has been measured in fairly constant intervals. 

Is that another way of saying the averages control how many dots you get?


The interval makes up the resolution. In you're case you've measured data
every 180 secs. So to graph a full day you could say the number of dots in
the graph would be:

No of seconds per day/ No of seconds per interval = 60*60*24 / 180 = 480 

Now that's the number of rows in your day average RRA Since you don't want
to average multiple points in that RRA, your RRA step = 1. The xff can be
set to 0.5   

How do you decide what xff to use?  What is it?  

People talk about rows...is the data in a row column format in the rrd?
With my data, how would the table look? 

You're base interval is 1800 secs, so that's the rrd stepsize.   

How do I use this 1800 stepsize ... this is different than the --step
parameter?  Do I need a --step 1800?  

Based on all this you should try: 

rrdtool create mailmon.rrd --start (first timstamp in your data)
DS:delivery:GAUGE:360:U:U RRA:AVERAGE:0.5:1:480  

I tried this and ran the graph command listed below.  I get a graph that has
week 47 - week 50 on the horizontal and 100 through 300 on the vertical.
Why did it talk about weeks when I put in a start of 0 hr today and end of
time I ran the command? 


-----Original Message----- 
From: David Edward Shapiro [ mailto:David.Edward.Shapiro at btitele.com
<mailto:David.Edward.Shapiro at btitele.com> ] 
Sent: Monday, November 19, 2001 11:16 PM 
To: 'rrd-users at list.ee.ethz.ch' 
Subject: [rrd-users] Newbie help need 

Could somebody please explain in layman terms some of these components? 

I have simple data: 

a date and a number (time mail went out, and seconds for it to return) 


What I did was collect this data for a couple weeks.  Today, I set utc_start
to equal 0 hr of today.  I have no idea what to set for counter or average
(ie., should I use 600, 200, etc.)  I also have no idea what to set for
average (1200, 1000000, 5, etc.).  I need some explaination so I logically
put in the right numbers.  I just wanted a graph showing today's data to
whatever time I run the script. The script uses 0 hr utc time and gets the
time that the script is run and converts that to utc time too.

rrdtool create mailmon.rrd --start $utc_start DS:delivery:COUNTER:600:U:U

When I create the graph, I used: 

rrdtool graph mailmon.gif --width 360 --vertical-label seconds --start
$start --end $last DEF:delivery=mailmon.rrd:delivery:AV

ERAGE LINE1:delivery#FF00000:delivery 

I set start to utc 0 hr today and set end to the last utc time of my data.
The graph shows on the horizontal week as a measure.  I did not expect that
at all.  I was  expecting 0 hr of the present date to whatever time I ran
the script.  I see M as a measure on the vertical.  No idea what that is.  

Please pelase help! 



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