[rrd-users] Re: Examples / Docs...

Alex van den Bogaerdt alex at ergens.op.HET.NET
Sat Aug 10 23:29:43 MEST 2002

Chris Knipe wrote:

> rrdtool create myrouter.rrd         \
>             DS:input:COUNTER:600:U:U   \
>             DS:output:COUNTER:600:U: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         \
>             RRA:MAX:0.5:288:797
> This is from the RRD tutorial, and has 600 samples of 5 minutes, 700 of
> 30minutes, 775 of 2hours and 797 of 1day.
> Now, to my understanding, I'd need to modify that, so that I have 228
> samples of 5 minutes (the last 24hrs),  1488 samples of 30 minutes (the last
> 31 days, or month), and 365 samples of 1 day (the last year).

You need nothing.  If you use these (or any other) values it is because
you want to.

What do you want?  You want to be able to query data in resolution 'r'
and for a timespan 't'.  You can do this only if you have data available
for timespan 't' *or*more*.  The resolution is not as important but it
helps RRDtool to quickly do its job. More on this later.

> This leaves me with a few questions...
> Firstly, I presume because my longest period is 365 1 day periods, that this
> database will only hold the information for 1 year.  If I wanted to archive
> it for the last two years, do I simply add another RRA with 730 samples of
> 1day?  And how will this affect the graph?

I don't see why you want to do that.  If you have an RRA with 730 rows,
you can fetch 365 of them, can't you?

What you can't do by the way is plot january 1st 2000 upto and including
december 31st 2001 with only 730 rows.  You need 731 rows (feb 29th !)

> Thirdly, why can't I simply use 210240 samples of 5 minutes (two years) and
> use 1 RRA?

You can.  RRDtool will have to do a lot of calculations at graph time
in stead of collection time.

 / alex at slot.hollandcasino.nl                  alex at ergens.op.het.net \
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