[rrd-users] rrdtool memory usage and the Raspberry Pi

Tobias Oetiker tobi at oetiker.ch
Fri Oct 16 08:19:40 CEST 2015

Hi Jared,

Today Jared Henley wrote:

> Hi,
> I've been working on a logging application that uses rrdtool.  It works
> brilliantly on my PC, not so good on the Raspberry Pi model B+.  But before I
> go there, there's something interesting I noticed while working on the PC.
> I'm creating a database with the following command (in rrdpython)
> rrdtool.create(filepath,
>     '--step', '1s',
>     'DS:progreset:GAUGE:1000s:0:1',
>     'RRA:MAX:0.1:5s:5000m',
> <snip - there are 29 definitions all up, all the same>
> This creates a 386MB file.
> I didn't think too hard about it, until I did a graph to a CSV file.  Of
> course the CSV would be less space-efficient than the binary rrd file, right?
> But the generated CSV turns out to be only 15MB?
> rrdtool seems to use 64-bit integers for everything, so I figure the rrd file
> above should use:
> 8 bytes per RRA entry * 29 RRAs + 1 timestamp * 60,000 locations in the
> round-robin (5000 minutes / 5 seconds) = 14.4MB.  I'm confused. Why is the rrd
> file 30 times bigger than I'd expect?  I did experiment with a step size of 5
> seconds, but the created file was the same size.  But I can live with largish
> files.

when I create this database on my intel box it looks like this:

oetiker>./rrdtool create /tmp/demo.rrd --step 1s DS:progreset:GAUGE:1000s:0:1 RRA:MAX:0.1:5s:5000m
oetiker>ls -l /tmp/demo.rrd
-rw-r--r-- 1 oetiker oep 480584 Oct 16 08:17 /tmp/demo.rrd

so something looks rather odd here ... are you using 1.5.4 on your
raspy ?

Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland
www.oetiker.ch tobi at oetiker.ch +41 62 775 9902

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