# [rrd-users] Questions about different RRA`s

Ryan Steele steele at agora-net.com
Fri Apr 6 17:00:21 CEST 2007

```David Schulz wrote:
> Yes ive seen Cacti, its nice. The whole idea for me though is to
> actually learn how the rrd thing works, so i am not limited to a
> front-end.
>

A very good idea!  I took the same approach, mostly because I was
unaware of Cacti when I first starting playing around with RRDTool.  I
did find helpful, when I was a bit green on the whole thing, two
tutorials on Tobi Oetiker's site, which are located at
http://oss.oetiker.ch/rrdtool/tut/rrdtutorial.en.html and
http://oss.oetiker.ch/rrdtool/tut/rrd-beginners.en.html respectively.
But, going to the examples you referenced:

RRA:AVERAGE:0.5:60:24

...means you'd have 24 consolidated data points (CDP's), with each CDP
being the average of 60 300-second (5 minute) intervals.

RRA:AVERAGE: 0.5:24:60

...means you'd have 60 consolidated data points (CDP's), with each CDP
being the average of 24 300-second (5 minute) intervals.

While it's true that:

300 * 60 * 24 = 432000 seconds = 120 hours = 5 days
AND
300 * 24 * 60 = 432000 seconds = 120 hours = 5 days

The representation on the graph will be different, because in the first
example, each CDP is the average of 60 intervals, while the second
example has each CDP being the average of only 24 intervals.

Make sense?

Best Regards,
Ryan
> Thanks a lot,
> David
>
>
>
> On Apr 5, 2007, at 10:08 PM, Ryan Steele wrote:
>
>
>> David,
>>
>> Just my two cents - check out Cacti.  It comes with lots of pre-
>> loaded RRD/RRA definitions, among them being the process counts.
>> Of all the frontends to RRDTool, I prefer Cacti over Munin,
>> Cricket, MRTG, and the like.  The documentation is a bit less than
>> you'd like, but once you get your head around it it's really a
>> dream to work with.
>>
>> Best,
>> Ryan Steele
>>
>> David Schulz wrote:
>>
>>> Hello,
>>>
>>> since a while i am digging around the Net to become more clear
>>> about  rrdtool, but i am not making much progress.
>>>
>>> My Goal is to graph the Number of Processes on my Server, for the
>>> last  hour, day, week, month and year. In the beginning i just
>>> made  one big Archive, using
>>>
>>> Can someone show me how to best create one such .rrd with
>>> multiple  RRA`s, explain to me the calculations you made to decide
>>> on the  values for the RRA`s? I tried multiple combinations, one -
>>>
>>> rrdtool create process_count.rrd --step 60 DS:pc:GAUGE:120:0:U
>>> RRA:AVERAGE:0.5:1:525960, which is supposed to take one value
>>> every  60 seconds, for one year,
>>>
>>> but it appears it is better to split the different required times
>>> into different RRA`s. I have no idea how to calculate this though.
>>> My  main Problem is to determine the exact Values for the
>>> individual  RRA:AVERAGE:0.5:?:?. I have read that for example this
>>>
>>> RRA:AVERAGE:0.5:1:60 should be one hour (1*60*60= 3600 seconds),
>>> and  RRA:AVERAGE:0.5:60:24 should be 24 hours, but how about a
>>> week or a  month for example? Why RRA:AVERAGE:0.5:60:24, and not
>>> RRA:AVERAGE: 0.5:24:60, both should equal a week, right?
>>>
>>>
>>> I really need a push in the right direction here.
>>> Thanks a lot for any Explanation,
>>> David
>>>
>>> _______________________________________________
>>> rrd-users mailing list
>>> rrd-users at lists.oetiker.ch
>>> https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users
>>>
>>>
>> --
>> Ryan Steele                         Systems
>>
>>
>>
>
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--
Ryan Steele