[rrd-users] How to calculate how much memory rrdtool needs to generate a graph

[Erik Freiholtz]

Hi!

I'm running rrdtool (1.0.50) on Openwrt. The system (Asus WL500GP) has 
only 32 Mb RAM and no swapspace.
At the moment I'm having 16 data sources (in separate databases) and I 
sample every 5 minute.

There won't be any other memory hungry processes run on the device.

The system will run in a remote location and will upload graphs to a 
remote server. When the system is installed I will have no access to it. 
(Well, I can drive 500km to get access to it...)

I really need to know how large timespan I can graph on this system. It 
will be a disaster if I the system crashes or stops to genereate graph 
after a couple of months because there is not enough memory. I can 
adjust the sample interval, but I want as good resolution as possible.

So, is there a simple way to calculate how much memory is needed to 
genererate graphs based on number of datasources, sample interval and 
timespan of the graph?

Best regards
Erik Freiholtz